HRV or ERV?

[nicholasa]

Building a Foam insulated house (very tight), so indoor air quality is a concern. The Foam insulator insist on a ventilator (HRV, ERV)

The concern is a build up of humidity in the winter when the house is closed up tight for 5 months.
(Maryland)

Currently an Aprilair ERV is being installed, but reading about them (aprilair ERV), They transfer the heat AND humidity to the incoming air in the winter time, thus retaining indoor humidity.

The Carrier ERV lit. states that it's core will, remove indoor humidity in the winter AND remove humidity from the fresh incoming air in the summer.

Is this possible ? I though an ERV transfered the humidity from the high to the low, no matter what.

But it sounds like the carrier acts as an HRV in the summer, and an ERV in the winter.

Any thoughts ?

Nick

[Carnak]

Originally posted by nicholasa
Building a Foam insulated house (very tight), so indoor air quality is a concern. The Foam insulator insist on a ventilator (HRV, ERV)

The concern is a build up of humidity in the winter when the house is closed up tight for 5 months.
(Maryland)

Currently an Aprilair ERV is being installed, but reading about them (aprilair ERV), They transfer the heat AND humidity to the incoming air in the winter time, thus retaining indoor humidity.

The Carrier ERV lit. states that it's core will, remove indoor humidity in the winter AND remove humidity from the fresh incoming air in the summer.

Is this possible ? I though an ERV transfered the humidity from the high to the low, no matter what.

But it sounds like the carrier acts as an HRV in the summer, and an ERV in the winter.

Any thoughts ?

Nick

In the winter, the dry air stream is the fresh air being brought in. The ERV will remove humidity from the indoor air being exhausted and tranfer some of it to the fresh air coming in so as not to over dry the home. I am only familiar with the venmar residential ERVs. On a rise in indoor humidity, a bypass port opens to allow indoor air being exhausted to bypass the energy exchange wheel until the indoor RH level drops. An HRV can overdry homes in more northern locartions than yours.

In the summer, a significant portion of the humidity of the fresh air is transfered to the dry air being exhausted. The HRV again does not transfer this humidity.

In your location I would recommend the ERV, however no comments on the carrier model. Companies like venmar and renewaire are way ahead on the technology, maybe carrier is relabelling someone elses machine.

[Xavier]

Read the literature very carefully, as I have in the past 15 years of watching the development of ERV and HRV they some times adjust the exchange of air from 1 to 1 to more out then in to accomplish some advertising gimmick! Then the home most have outside air enter “uncontrolled!”

Furthermore no ERV or HRV is designed to ADD air to a home!!

[Carnak]

Originally posted by Xavier
Read the literature very carefully, as I have in the past 15 years of watching the development of ERV and HRV they some times adjust the exchange of air from 1 to 1 to more out then in to accomplish some advertising gimmick! Then the home most have outside air enter “uncontrolled!”

Furthermore no ERV or HRV is designed to ADD air to a home!!

I know reading comprehension is difficult for you, but read the original post very carefully X. This will be a well insulated and tightly constructed home, something which you have only read about but have never experienced.

There will be minimal infiltration in this type of home, so controlled mechanical ventialtion is required.

You never seem to grasp this concept.

This is not a drafty home where the positive pressure gimmick you sell, would be of any use except as an aesthetically pleasing combustion air intake. In fact of all the partial quotes listed on your site, the only good thing it says about your product is that it makes a good combustion air intake.

You also have only read about HRVs and ERVs and yet because they are competition for the POS positive pressure ventilation device that you sell, you always criticize them even though you do not totally understand them.

How are the old ROI's coming along with the price of energy these days?

[teddy bear]

The new super tight and insulated homes has series of needs that current HVAC systems may not deal with. We use cloths drier, bath fans, kitchen hood, water heater, fireplaces, and central vac that need make-up air. The sensible cooling load is much less than normal which leaves a high latent cooling ratio,(moisture). Make-up air ventilation with dehumidification is the best system for green grass/humid climates. You provide the filtered make-up air required for the various mechanical appliances and purging indoor pollutants. These systems also filtering and controlling the humidity of the entire home winter and summer. In NE U.S. during winter, there a $50 increase in heating compared to HRV/ERV. During summer, you break even because of higher thermastat set points. Controlling humidity makes entire home vary comfortable including the basement.

[nicholasa]

Thanks TB,

Still trying to finish off this house.
(2 Bryant infinnity systems, and 1 april air ERV up stairs)

I am adding an Ultra-Aire Dehumid to the basement/1st floor system. can't find ANY local Ultra-aires, only April-aire units, guess I'll have to have 1 shipped.

My problem with the ERV's in general is that they "recover" indoor humidity in the winter, Not what I need in this tight house. BUT carriers ERV claims to remove humidity from the indoors in the winter too ???

http://www.xpedio.carrier.com/idc/groups/public/documents/marketing/08er-v00-042104.pdf

As far as controlling make-up air, does any one make a controller with inddor and outdoor pressure sensors ?
So the fresh air damper would open only as needed ?

This being a tight house with UNVENTED cathedral ceilings, I donot want to over pressurize in the winter, thus forcing warm/moist interior air in contact with cool exterior surfaces, My aim is nuetral pressure.

Thanks,
Nick

[Carnak]

[Edited by Carnak on 09-06-2004 at 08:18 AM]

[teddy bear]

Originally posted by nicholasa
Thanks TB,

Still trying to finish off this house.
(2 Bryant infinnity systems, and 1 april air ERV up stairs)

I am adding an Ultra-Aire Dehumid to the basement/1st floor system. can't find ANY local Ultra-aires, only April-aire units, guess I'll have to have 1 shipped.

My problem with the ERV's in general is that they "recover" indoor humidity in the winter, Not what I need in this tight house. BUT carriers ERV claims to remove humidity from the indoors in the winter too ???

As far as controlling make-up air, does any one make a controller with inddor and outdoor pressure sensors ?
So the fresh air damper would open only as needed ?

This being a tight house with UNVENTED cathedral ceilings, I donot want to over pressurize in the winter, thus forcing warm/moist interior air in contact with cool exterior surfaces, My aim is nuetral pressure.

Your current local a/c company can get you a Ultra-Aire system. Regarding winter humidity, ERVs recover a portion of moisture from the outgoing exhaust air, roughly 50%. They will dryout the home but require more operation than HRV, makeup air, or exhaust air.

Regarding neutral pressure, with no ventilation the neutral pressure is midway between the top and bottom of the home. The top of the home is positive pressure and the bottom is negative. The colder the outside temperature, the greater the positive and negative pressures. At +15^F, a very tight 3,000 sq.ft. home leaks 50 cfm of inside air out through the high part of the home including the catherdral ceiling. An equal amount of fresh air infiltrates low in the home like around the rim joist. An HRV/ERV does not change the neutral point but adds to the air change rate. Exhaust ventilation like bath fans, clothes drier, and kitchen fans raises the neutral point and decreases the exfiltration. Make-up air ventilation like Ultra-Aire increases the exfiltration through the ceiling. Ideally, use make-up ventilation during the spring/summer/fall and exhaust ventilation during cold weather. The most critical issue is keeping the home dry enough to avoid condensation of exfiltrating air in the catherdral ceiling. The rest is your choice.

[Carnak]

Yes some positive pressure with air brought in through the dehumidifier would be good in the summer. Dehumidifier is not really designed to control humidity in winter application, temperatures and RH levels too low.

A switch to exhaust ventialtion, even wired in to a dehumidistat creating a slight negative in winter would not be a bad thing especially if the heating appliances were direct vent, and there was no problem with radon.

Slight positive in summer and slight negative in winter keep humid air out of wall cavities.

System would work great as long as there is no big exhaust appliances like a Jenn Air, its just that it is expensive operate.

X will be foaming at the mouth about now.

Commercially, ERVs and HRVs are run out of balance to maintain the desired positive/negative pressures.

The residential ERVs that I have installed in Canada, use a bypass port. On a rise in indoor RH above the setpoint, the port opens and air is exhausted temporarily without the heat/moisture transfer to the fresh air. It allows constant fresh air with as much humidity as the windows can take.

HRVs when run steady will over dry a home, where as the ERV will not.

[nicholasa]

And You just know a JennAir is going in this house :)

The AprilAire ERV is a continous run type unit, with dampers to adjust for neutral pressure.

Could I adjust the dampers to run out of balance in the winter, creating a neg pressure during the heating season ?

Then the Ultra-Aire Dehumid w/fresh air intake would run in the summer creating a pos pressure ?

The kitchen and laudry are back to back, I am thinking about a dampered 6" fresh air make up for this area, Wired into the JennAir and dryer.

Wood stove/ pellet stove will have its own combust air intake., Water htr, HVAC, etc all electric, so no back drafting problems in the winter ?

Also What is the ideal indoor RH while the outside temps are in the 20's, so that condensation will not be a problem ?

Carnak,
Will the Ultra Air not help with winter time indoor RH ?

Thanks,
Nick

[Xavier]

As far as controlling make-up air, does any one make a controller with inddor and outdoor pressure sensors ?
So the fresh air damper would open only as needed ?



Yes there is!


"It is easy to be humble, when you are perfect!"

[Carnak]

All electric HVAC, electric water heater, DIRECT VENT wood stove where combustion air is directly ducted to the stove, no problems with downdrafting. I would not recommend a pellet stove that drew air from the house and an indirect combustion air intake that allowed cold air into the house.

Jenn Air in a tight house needs a make up air damper interlocked with the Jenn Air fan. Recommend dumping the air into an area of basement where there are no water pipes in the vicinity. I have never had problems with an intermittent dryer exhaust, but you could also interlock with the damper. Try not to cook and dry laundry in the winter at the same time in the winter or X will break a window on your house. :)

Make sure there is no Radon problem where you are.

Your ideal RH will be determined by your windows. The better the window, the warmer the inside surface temperature, the more humidity you can have.

I would avoid windows with metal frames or metal spacers between the panes as these short circuit heat out of your house and will be very prone to U shaped condensate patterns around the bottom of the window.

Glass with an R-value of 2 or better would allow you 40% RH (actually higher) in your winter climate. I would not recommend anything higher than 40%.

TB's system with the dehumidifier with fresh air intake in summer, and negative point exhaust in the winter is an alternative to using an ERV. The dehumidifier is designed for warmer more humid air in the summer time, especially with the fresh air intake. Using it in the winter time, the air is cooler inside the house. You would have to damper off the fresh air intake as well. The dehumidifier could frost up in the winter, at least it would in a colder climate like Canada. Therefore the dehumidifier would control summer time humidity and the exhaust fan would control winter time humidity.

You could be prone to prolonged periods of mild temps and high humidity and you may want a humidifier.

How about a link to your april air ERV before I comment further?

[nicholasa]

Carnak,

http://www.aprilair.com/product.asp?ID=C80A4BDAF31E426399117EFAF5F263B5&categoryID=9DDC176A7AD948DCB0D14F348EB3FF1e

I am thinking of going with a HRV instead, for winter time use only. It will keep the winter time indoor RH lower than an ERV will ? I am told that You can rot a super tight house out in the winter (from the inside out), if You do not ventalate and keep the RH down.

Xavier,
Do You have a link to the damper control with differental pressure sensors ?

Thanks,
Nick

[Xavier]

Nick, if you want to know more about a poster you can click on the icons at the bottom. One will show bio info others may have a web site with links etc.

Continue your research, click at the bottom of ALL posters and good luck.

I am off shipping units now that utility bills are UP, but will reply with data to your questions so you can compare the advice.

One final point, the best home is one that has NO Delta P between inside or outside summer and winter! This home will reduce the possibility for Radon and Mold! I think that perhaps some of the posters must have "positive pressure somewhere"!!!!

[Carnak]

Originally posted by Xavier


One final point, the best home is one that has NO Delta P between inside or outside summer and winter! This home will reduce the possibility for Radon and Mold! I think that perhaps some of the posters must have "positive pressure somewhere"!!!!


X , from a functional viewpoint, I see no difference with your product or going to Home Depot and buying two air intake hoods, ducting one to the return air of the furnace and use the second one as a combustion air intake. Ignoring function then, I see three differences. Your product costs more, you only have to cut one hole in the wall, and maybe you have deisgner colours that may look better. Flapper my a$$.

When the furnace fan runs you are pressurizing the space and when it is off, you are providing a parallel path to the building envelope as the space goes naturally negative. You average the positive and negative cycles and call this neutral?

Measure some airflows through your device and post them to prove me wrong. No natural stack effect just yet, but I will remind you again in January. I have asked you this on several occassions over the past couple years and it would be so easy to post some numbers if you had them to prove me wrong and make me eat crow, but you never do, because you have no clue as to what your device does.

If you control pressure, you control the flow of air through the building envelope and you can prevent air from contacting surface cool enough to cause condensation.

This is a very common practise in commerical, educational and institutional buildings.

The link below is a long one and is geared towards a hot humid climate, however it would apply to any summer time home where you run air conditioning. You have seen this link before, scroll down and read about pressurization.

http://www.fsec.ucf.edu/bldg/science/mold/index.htm

You should market your product in Florida. On a small house add the instruction "Connect one duct (or hose as you call them) to the return air ductwork,and plug the second opening." For larger house "Connect both hoses to the return". One size fits all. What a marketing strategy. Hell if you make them real pretty and drop the price I will distribute them in the Caribbean for you.

[Carnak]

Originally posted by nicholasa
Carnak,

http://www.aprilair.com/product.asp?ID=C80A4BDAF31E426399117EFAF5F263B5&categoryID=9DDC176A7AD948DCB0D14F348EB3FF1e

I am thinking of going with a HRV instead, for winter time use only. It will keep the winter time indoor RH lower than an ERV will ? I am told that You can rot a super tight house out in the winter (from the inside out), if You do not ventalate and keep the RH down.

Xavier,
Do You have a link to the damper control with differental pressure sensors ?

Thanks,
Nick

I looked at the unit and it is similar to an HRV, but the core also allows moisture transfer. I am trying to figure out if it has a means of temporarily bypassing the humidity exchange.

An HRV will work hard the first winter after the house is built, drying out all the moisture from new construction. During the second winter, you will find that it will over dry your home and a means of avoiding this is to run the unit intermittently, via the standard controls, so that it kicks on as RH rises. This will usually give decent IAQ.

The ERV should allow you the luxury of the constant fresh air, without overdrying the home, and give you the maximum IAQ possible.

[nicholasa]

Heres another thought on the ERV/HRV debate.
On the manufactures climate maps (that show where ERV or HRV's should be used, by climate). HRV's are for way up north, but ERV's are recomended for most of the US.

Now I understand that ERV's would be needed for area's that have a long cooling season, so as not to introduce to much humidity. But if HRV's are drying out houses to much up north, why are they not recomending ERV's up there ?? they would retain 50% of the indoor RH. or is this to wet in a tight house ???

I am getting a new Bryant unit that works with the infinity controller. but I cant make a decision HRV or ERV.

Nick

[Carnak]

The HRVs and ERVs go into defrost mode. The HRV will frost up only on the exhaust side, the ERV because it transfers moisture would tend to freeze up on both sides.

The HRV has a condensate drain while the ERV does not. The drain is for when the core freezes up. Wheel type of ERVs are used in Canada but they are no where near as common as the HRV up there.

Where you are the ERV will be fine, to give you peace of mind, you will want one that can temporarily bypass air when humidity gets too high in winter.

[goldenear]

I'm a bit late to this thread but I'll provide a bit more info in the event that it is still timely. First, just about all of the HRV's and ERV's distributed in North America are built either by Venmar or Lifebreath. Companies like Bryant, Lennox, Broan, Carrier, etc. just rebadge these manufacturers' boxes. Second, most of the info here is correct, but I feel some explanation is in order.

I think there is a general assumption that ERV's exchange latent energy on a 1-1 ratio. TB mentioned a 50% exchange ratio. Well with certain ERV's, neither is true. I've seen figures as low as 26%. Most of the variation can be accounted for in the design (wheel vs. counterflow/crossflow core). The very best way to screen products for a specific application is to evaluate the figures posted in the product directory found on hvi.org's site. You'll also see the redundancies with respect to products from various manufacturers vis-a-vis Venmar & Lifebreath. It's quite amusing actually because the spec's are absolutely identical. Not a single variation!

With respect to nicholasa's application, I agree with Carnak that an ERV would be beneficial, however, I wouldn't recommend a common ERV like the AVS Duo from Venmar because it transfers too much latent energy (if indoor RH during heating season is primary concern). Instead, search the numbers for an ERV that is still fairly efficient with respect to sensible load (apparent sensible effectiveness) but decreases latent recovery % as the temp falls or cfm increases (preferably both). Guess what? There exists such a unit made by Venmar for VanEE called the 2001ERV. Unfortunately, that product is only available in Canada. BUT, look closely through the sheets in that product directory and BINGO you'll find the exact same spec's from a Broan/Nutone ERV200HC. There you go, the exact same product available domestically. I would assume that the Carrier ERV is, in fact, this very same unit, all originating from Venmar. Check the spec's @ hvi.org to confirm. For the best info about this piece, go to VanEE's web site and look at the Gold Series ERV's. This site has the most detailed info available.

But the real incredible feature with this piece is that it is fully convertible. Simply swap cores and remove a jumper on the circuit board, and you've got the 2001 HRV. Brilliant design. You just can't go wrong with this unit in the U.S. heating climates where a SEVERE moisture problem in the heating months is not apparent. For humid, cooling climates, the latent recovery efficiency probably won't cut it, so one would need to look elsewhere.

[Edited by goldenear on 10-07-2004 at 07:18 PM]

[Ben4ZEH]

Goldenear,

Not sure if you'll get this, but I would really like to hear how you feel about ERV vs. HRV today. Unfortunately, not much has changed in the ERV/HRV market, but I've seen a few exceptions of advancements.

I will decide between an ERV/HRV in a newbuild located in Denver, CO. My greatest concern is interior condensation in the winter. I won't run AC in the summer, so there is little benefit of an ERV during "cooling" months.

Very curious to hear what you like these days.

Thanks,
Ben

[goldenear]

Hey Ben,

I agree that not much has changed in ERV/HRV over the past few years, and I consider that to be a GOOD thing (except more companies are trying to manufacture their own models - pro's and con's to that one). I'm still using the relabeled VanEE model from Broan and it's excellent. I've considered reinstalling from a volume to a more dedicated install because interlocking it with the furnace fan is definitely more costly over the long run. Plus, people wouldn't complain about the drafts in the winter; but have not done so yet. The one thing I like about my install currently is that fresh air is hitting the furnace media filter before getting into the air envelope of the home. The filter that comes with the unit I have is basically a bug screen, so it does nothing to help my family with their allergy issues. The HEPA units solve this problem.

I don't know what your typical dew points are in the winter months in Denver, but I'd guess that they're relatively low. During the past week here in WI, we have experienced some of the harshest dry air that I can ever remember (I'm 35). This week, the dew point has averaged something around -15F! Holy #*(%. Talk about miserable. I cannot imagine the pain and suffering people who live in loose homes are feeling right now. Heated to 68-70F, some loose homes with no humidification could be sitting in single digits indoor RH! I think my nose would fall off.

And if you ran an HRV under these conditions, you'd create a comparable indoor RH because you're not exchanging any moisture content upon air exchange. Even with an ERV, I've had to basically turn it off because the conditions are so extreme and I don't have a humidifier installed - will probably pick one up so the next time this happens, I'll be ready. Even with a very tight home and no exhaust fan use of any kind except intermittent use of a clothes drier, we're still down to ~35% indoor RH!

So I'd say better go with the ERV. You'll lose some of the recovery efficiency in winter compared to an HRV, but you'll be more comfortable, esp if running continuously. Of course, you could always go the HRV route combined with a humidifier if heating expense was super high. If you picked up the same model I have, you could actually buy the HRV core and swap cores whenever you wanted to convert the machine. But if heat recovery is THAT much of an issue ($$$), then it'd be better to get a unit with a very large core to increase efficiency (probably wouldn't be convertible, so you'd have to install the humidifier as well).

Regarding summer use, if you ventilate with open windows, then yeah, not much need to go mechanical. But as soon as you close up that house, then there's a huge benefit in terms of IAQ to run the system.

Hope this helps...

[seadragon]

I live near Toronto, Canada and have the Van-EE Gold 1001 ERV. It actually was an HRV model when I bought it, but I since bought the ERV core and converted it over.

I found the HRV brought in too much humidity in the summer. So much so, that I just turned it off for the summer. By the next summer, I had installed the ERV core. Big difference. I can now run the ERV year round and humidity levels are in check. I still have to use dehumidifiers in the basement of course, but they cycle on and off instead of running constantly when I had the HRV core.

So in the end I found the ERV to be more suitable.

[teddy bear]

Hey Ben,

And if you ran an HRV under these conditions, you'd create a comparable indoor RH because you're not exchanging any moisture content upon air exchange. Even with an ERV, I've had to basically turn it off because the conditions are so extreme and I don't have a humidifier installed - will probably pick one up so the next time this happens, I'll be ready. Even with a very tight home and no exhaust fan use of any kind except intermittent use of a clothes drier, we're still down to ~35% indoor RH!

Hope this helps...
Good post! One point you are illistrating is the lack of the need for mechanical venilation during cold dry weather. If no mechanical ventilation is required during the only time heat energy is saved, what is the benefit? Clothes driers, kitchen hoods, water heaters, and bath fans need make-up air to function. Balance flow ventilation ERV/HRVs takeout as much air as they bring in, therefore no help. Homes need more fresh air during the neutral weather. They need make-up air for other exhaust devices to function. Homes need supplemental dehumidification during times of low/no cooling load conditions to avoid biological growth. To me, most homes are better served by a ventilating dehumidifier. HRV/ERVs are a must for extremely tight homes in cold climates with high cost electric heat, and high ventilation needs. We sell both. TB

[Carnak]

The ventilation is needed in the coldest weather in the tight homes, otherwise you end up window condensation.

If the home is dry in the coldest weather and actually needs a humidifier, it does not need ventilation, the infiltration is plenty

Supplemental dehumidification in the summer can be a neccessity in some homes or band aid repairs in others.

[goldenear]

Well dry is a relative term, right? For me personally, the past couple of weeks have brought the coldest, driest air that I can ever remember. This has been a brutal beginning to February, so much so that I'm thinking of moving, lol. In order for my house to avoid condensation on the windows right now, I'd have to maintain an indoor RH of probably <20%. That's great for the house but horrible for us humans.

Ask any otolaryngologist about indoor RH during the heating months and they're going to tell you to definitely keep it above 30%, preferably no lower than 40%. So there's a conflict between the building scientists and the medical professionals. Some people can get away with temporary bouts of extremely low indoor RH. Others like me who have really bad vasomotor rhinitis, which seems to triggered by large swings in RH, temp, and barometric pressure, or those who have a house full of occupants with viral and bacterial upper respiratory infections, have little choice but to say to heck with the wooden casement windows - let 'em rot in winter, I'll fix 'em in the spring.

Windows really are the weak link in the building envelope, assuming everything else is properly sealed and insulated. Unfortunately, if you don't build, then you're stuck with whatever came with the house (usually inadequate even in new construction) and that will ultimately determine your indoor RH if you're absolutely committed to maintaining a condensate free interior.

[goldenear]

Good post! One point you are illistrating is the lack of the need for mechanical venilation during cold dry weather. If no mechanical ventilation is required during the only time heat energy is saved, what is the benefit?

I agree, but here in southeast WI, the past stretch of 10-20 days has been an extreme and definitely not the norm for the 6-7 months of the heating season (Oct-Mar/Apr). So you've got, at the most, one month out of let's say avg. of 6.5 months that there's no ROI on an HRV (ERV is beneficial the remainder of the yr in this climate, esp with a family affected by seasonal allergies, so opening windows is not advised).

[Carnak]

Well dry is a relative term, right? For me personally, the past couple of weeks have brought the coldest, driest air that I can ever remember. This has been a brutal beginning to February, so much so that I'm thinking of moving, lol. In order for my house to avoid condensation on the windows right now, I'd have to maintain an indoor RH of probably <20%. That's great for the house but horrible for us humans.

Ask any otolaryngologist about indoor RH during the heating months and they're going to tell you to definitely keep it above 30%, preferably no lower than 40%. So there's a conflict between the building scientists and the medical professionals. Some people can get away with temporary bouts of extremely low indoor RH. Others like me who have really bad vasomotor rhinitis, which seems to triggered by large swings in RH, temp, and barometric pressure, or those who have a house full of occupants with viral and bacterial upper respiratory infections, have little choice but to say to heck with the wooden casement windows - let 'em rot in winter, I'll fix 'em in the spring.

Windows really are the weak link in the building envelope, assuming everything else is properly sealed and insulated. Unfortunately, if you don't build, then you're stuck with whatever came with the house (usually inadequate even in new construction) and that will ultimately determine your indoor RH if you're absolutely committed to maintaining a condensate free interior.

You need better windows then. NW Ontario they can maintain 35% when its minus 30C

[teddy bear]

I agree, but here in southeast WI, the past stretch of 10-20 days has been an extreme and definitely not the norm for the 6-7 months of the heating season (Oct-Mar/Apr). So you've got, at the most, one month out of let's say avg. of 6.5 months that there's no ROI on an HRV (ERV is beneficial the remainder of the yr in this climate, esp with a family affected by seasonal allergies, so opening windows is not advised).
Consider that a home that gets enoughfresh air during the coldest months requires only small amount supplemental fresh air during the milder winter months. You are dealing with small amounts supplemental fresh air with small temp differentials during mild weather. Therefore the payback is much reduced. The energy saved is less than $100 for the year when compared to an optimized simple make-up air ventilating system. My concerns are that after spending a lot of money for a hrv, most will not provide fresh air ventilaiton during summer while maintaining <50%RH. Regarding IAQ, summer fresh air with <50%RH is much more critical supplemental winter ventilation. Dust mites and mold cause more IAQ problems a little window condensation. Do both if you have the money, but do not neglect summer needs. TB

[Carnak]

My cousin married a chiropracters daughter.

Her father used to crack her back when she had a cold, quite a cure all

[regulajo]

I am wondering about how to attain replacement or fresh air in an ICF constructed home. ERV or HRV?
Also, if humidty is something to be too concerned with in a tight home in Utah, the second driest state in the nation. (our skin gets so dry here, we all look like lizards in the winter).
The home is designed around passive solar gain in winter for some heating, radiant heating in concrete slabs.
Passive breezes through open windows for summer cooling. (It will have ducts for air conditioning system).
Any help or suggestions would be appreciated.
Steve

[teddy bear]

I am wondering about how to attain replacement or fresh air in an ICF constructed home. ERV or HRV?
Also, if humidty is something to be too concerned with in a tight home in Utah, the second driest state in the nation. (our skin gets so dry here, we all look like lizards in the winter).
The home is designed around passive solar gain in winter for some heating, radiant heating in concrete slabs.
Passive breezes through open windows for summer cooling. (It will have ducts for air conditioning system).
Any help or suggestions would be appreciated.
Steve

You live in an arrid climate winter and summer. Probably with the clothes drier, bath fans, and kitchen hood in 2,500 sqft. 4 people, 75 cfm of fresh infiltration will be ok. Get good bath fans that you can operate extra hours during the coldest weather for extra boost. Any wood burners or fireplaces. If yes suggest some make-up air to assist the chimineies. TB

[regulajo]

Teddy,

Thanks for your reply. Here are a few more details.

The home is two levels, main and lower, 4000 square feet total with five people and a dog. It wiill have a gas burning fireplace on the main floor. The bath fans, 4 of them, will be very good, I believe they are about 200 CFM each and will vent outside the home.
The kitchen range hood, centrally located in the homes main floor, is rated up to 1400 CFM on high, although I doubt we will run it on high very often.

Any other suggestions or ideas would be appreciated while we are still in the design phase.

Thanks again,
Steve

[goldenear]

You need better windows then. NW Ontario they can maintain 35% when its minus 30C

Have known this for some time now. These are Hurd casement windows and there really aren't any better options here in the States. What brand are you talking about and are those wooden casement windows?

[goldenear]

The bath fans, 4 of them, will be very good, I believe they are about 200 CFM each and will vent outside the home.
That number seems a bit high. Average vent rating for bath fans is about 75 CFM. Regardless, with that size of a range vent, you're going to need makeup air because even deliberately running a 200 CFM ERV out of balance (something no manufacturer would ever "officially" recommend), it won't come even remotely close to balancing your home's air envelope.

An HRV doesn't make any sense for you because, assuming you'll provide secondary humidification at least during the heating season, it will just suck out all of the moisture that you introduce into the air. If it were me, I'd ditch the bathroom vent fans altogether and source point ventilate all of them instead, ducting each one into an ERV to recover as much moisture and heat as possible which will transfer that energy to the incoming fresh air.

[pstu]

>>The kitchen range hood, centrally located in the homes main floor, is rated up to 1400 CFM on high

I wonder what kind of ducting you have for a fan of that capacity? Just trying to learn. The more I learn about ducting, the more I feel the need to respect its problems.


With those bath fans, sounds to me like you might easily see 1000 cfm total exhaust, with a tight house that sounds interesting. I'm sure there is a simple and probably elegant solution to keep your chimney from being the intake shaft.

Best of luck -- Pstu

[teddy bear]

Teddy,

Thanks for your reply. Here are a few more details.

The home is two levels, main and lower, 4000 square feet total with five people and a dog. It wiill have a gas burning fireplace on the main floor. The bath fans, 4 of them, will be very good, I believe they are about 200 CFM each and will vent outside the home.
The kitchen range hood, centrally located in the homes main floor, is rated up to 1400 CFM on high, although I doubt we will run it on high very often.

Any other suggestions or ideas would be appreciated while we are still in the design phase.

Thanks again,
Steve

Forget about ERV/HRV. You biggest problem will be operating all that exhaust equipment. Make sure all of the gas appliances are power exhaust to avoid backdrafting. You may need powered make-up at least for the kitchen hood. Maybe a custom designed make-up air on your furnace?? Only operate the on high with window/door open. Most do onle 50% of claim. That's still to much. You need a good a/c designer. A scared TB

[goldenear]

The more I think about your situation, the more I believe these "who can produce the biggest residential kitchen vent" contests to be an exercise in complete futility. No residence on Earth needs 1400 CFM of exhaust unless you're doubling as a commercial food preparing facility. Even then, that's overkill for that size of a space.

My wife can cook the most obnoxious smelling food (not her cooking, lol, just the nature of the food material) without using ANY kitchen exhaust, and I can have the entire house cleaned out in a couple of hours using a 200 CFM ERV (not even installed in source point vent - just simplified volume). This is a 2500 sq ft ranch with the same layout in the conditioned lower level, so 5000 sq ft total (main floor 9' ceilings with cathedral great room and lower with 8' ceilings, so that's a decent amount of air).

Although that's not the ideal method, it just goes to show you that these ridiculous kitchen vents are simply not needed in residential applications. People are being oversold everyday on these stupid things. But the real story is they cause more problems in terms of balancing the home's air envelope than is necessary.

[Xavier]

“With those bath fans, sounds to me like you might easily see 1000 cfm total exhaust, with a tight house that sounds interesting. I'm sure there is a simple and probably elegant solution to keep your chimney from being the intake shaft.

Best of luck – Pstu”

Yes there is a KISS solution—however, it is very high tech and complicated, it is called “opening the kitchen window” when the fan is on and don’t stand in the way of the air flow (wind chill)!!!! My window and ERV/HRV comments which you so often do not understand are supported by the following posts!


teddy bear " Forget about ERV/HRV. You biggest problem will be operating all that exhaust equipment. Make sure all of the gas appliances are power exhaust to avoid backdrafting. You may need powered make-up at least for the kitchen hood. Maybe a custom designed make-up air on your furnace?? Only operate the on high with window/door open. Most do onle 50% of claim. That's still to much. You need a good a/c designer. A scared TB

goldenear “My wife can cook the most obnoxious smelling food (not her cooking, lol, just the nature of the food material) without using ANY kitchen exhaust, and I can have the entire house cleaned out in a couple of hours using a 200 CFM ERV (not even installed in source point vent - just simplified volume). This is a 2500 sq ft ranch with the same layout in the conditioned lower level, so 5000 sq ft total (main floor 9' ceilings with cathedral great room and lower with 8' ceilings, so that's a decent amount of air).”

You failed to identify the cost to "condition" the 24,000 cubic feet of outside air you are exchanging in the two hours as a factor too!

To avoid the requirement for large kitchen range exhaust fans, I think they invented outside barbecues!:)

[goldenear]

You failed to identify the cost to "condition" the 24,000 cubic feet of outside air you are exchanging in the two hours as a factor too!

And you failed to identify the cost to condition the outside air flowing through your open window to balance the air envelope while running all of the exhaust vents. ;) Our kitchen doesn't have any windows since it is in the center of the home - just a patio door. During the past couple of days, if I had to open that door while cooking, the kitchen would have been full of snow. The average lot size in our neighborhood is 3 acres and when it snows, it often falls horizontally because there aren't any metropolitan structures to block the howling wind. Right now, there's a six foot high snow drift in front of our front porch.

You're obviously absolutely correct, though. And that's why we use an appropriately sized kitchen vent to exhaust the odors before they permeate throughout the home. I simply provided this example to illustrate the "retardedness" of using commercially sized kitchen vents in typical residential applications.

[goldenear]

Good post! One point you are illistrating is the lack of the need for mechanical venilation during cold dry weather. If no mechanical ventilation is required during the only time heat energy is saved, what is the benefit?

I was re-reading this thread and just want to comment on this point for any future readers. The largest reason that our indoor RH was kept in check in February without running the ERV was because the builder ducted a fresh air/make up air supply duct to the return plenum. So every time the furnace fan operated, cold, dry air was being sucked into the return. This is the cheap way (upfront, energy costly in long-run) to provide air exchange and is completely unnecessary except for make up air after I installed the ERV. So, I will be installing a Belimo actuated damper tied into the Vision Pro IAQ to close off that hole in the wall unless there is demand for make up air. After doing this, mechanical ventilation will be required.

[teddy bear]

I was re-reading this thread and just want to comment on this point for any future readers. The largest reason that our indoor RH was kept in check in February without running the ERV was because the builder ducted a fresh air/make up air supply duct to the return plenum. So every time the furnace fan operated, cold, dry air was being sucked into the return. This is the cheap way (upfront, energy costly in long-run) to provide air exchange and is completely unnecessary except for make up air after I installed the ERV. So, I will be installing a Belimo actuated damper tied into the Vision Pro IAQ to close off that hole in the wall unless there is demand for make up air. After doing this, mechanical ventilation will be required.
Keep in mind that closing the make-up air inlet when the fan is not operating will save less than $10 for the year. Very little air moves through a small inlet with the fan off.
Unless you have a furnace with a gravity chiminey, close the make-up air on the cold air return and operate you ERV a little more. Keeping the vent closed all the time will save $50 for the year and you do not need the Belimo. Keep us posted on the summer %RH during wet weather. Only tring to help. TB

[goldenear]

yeah, key phrase in your statement being "when the fan is not operating!" However, everything connected to the system currently engages the fan. Also, everyone always says there's no infiltration through make up air duct unless house is in negative pressure. That's just plain wrong. When I was installing the Aprilaire 600, I stuck my hand in the drop and felt a lot of cold air pouring into the return plenum. The smell of cold, outside air was unmistakable. Everything was powered off, so no fan running. I think most of the infiltration is due to excessive wind in our area. 15+ mph is almost a daily average - kinda ridiculous. As soon as I installed the damper, no more cold, outside air. I also noticed the breaks between furnace cycles were significantly longer while running accessories such as ERV and humidifier that engage the furnace fan. That results in a direct energy savings.

Summer RH is handled by AC. Excess humidity when no demand for cooling will be handled by a UA 100V.

[teddy bear]

yeah, key phrase in your statement being "when the fan is not operating!" However, everything connected to the system currently engages the fan. Also, everyone always says there's no infiltration through make up air duct unless house is in negative pressure. That's just plain wrong. When I was installing the Aprilaire 600, I stuck my hand in the drop and felt a lot of cold air pouring into the return plenum. The smell of cold, outside air was unmistakable. Everything was powered off, so no fan running. I think most of the infiltration is due to excessive wind in our area. 15+ mph is almost a daily average - kinda ridiculous. As soon as I installed the damper, no more cold, outside air. I also noticed the breaks between furnace cycles were significantly longer while running accessories such as ERV and humidifier that engage the furnace fan. That results in a direct energy savings.

Summer RH is handled by AC. Excess humidity when no demand for cooling will be handled by a UA 100V.
I knew there was something I really liked about you. My point about a ducted fresh air inlet is about $10 worth of heat is required for the additional fresh air leaking into the home. Damper is ok. Saves $10/year. The average wind in WI is 7 knots/hour but location of the home and vent is everything. You have all the bases covered. Keep us posted on how your house works this spring/summer.
Thanks again, TB

[goldenear]

TB - well spring and summer have passed us here in WI. I still have not got around to installing the Ultra Aire unit but will need to do so relatively soon since I am framing in the utility room and need to have things finalized prior to completing the rough carpentry work.

The weather this year in SE WI has been all over the map as you know. No probs with indoor RH as monitored by the VisionPRO IAQ. Indoor temps were maintained @ 76-77F and RH was <50% with intermittent use of "basement" dehu in conditioned lower level. Yes, it's extremely energy inefficient and will be decommissioned soon.

ERV has been on continuous probably 65% of the time, 35% intermittent. Have used makeup air vent as needed based upon exhaust use. Have opened windows less than 5x this year. Our indoor air is cleaner than outside air.

[wetwindows]

I stumbled across this forum 3 days ago. It has exactly the info I've been wondering about.

I also live in SE Wisconsin and am planning on installing a renewaire erv. My question is sizing the erv. I have a house with a vaulted ceiling and walkout finished basement.

The upper level of the house 2400 ft2. The basement heating and cooling is not optimal as there are only two heat vents, no returns. Assuming I will not change anything in the basement regarding forced air heat, do I size the erv for the 2400 ft2 upstairs or do I include the basement too?

the units I am looking at are the ev130 (handles 2700 ft2) or the ev200 which handles an area >2700ft2.

side note: the ev200 seems a bit more energy efficient, but I don't really understand the numbers... http://www.renewaire.com/for_your_home/what_product_fits_you.php

thanks in advance.

[teddy bear]

I stumbled across this forum 3 days ago. It has exactly the info I've been wondering about.

I also live in SE Wisconsin and am planning on installing a renewaire erv. My question is sizing the erv. I have a house with a vaulted ceiling and walkout finished basement.

The upper level of the house 2400 ft2. The basement heating and cooling is not optimal as there are only two heat vents, no returns. Assuming I will not change anything in the basement regarding forced air heat, do I size the erv for the 2400 ft2 upstairs or do I include the basement too?

the units I am looking at are the ev130 (handles 2700 ft2) or the ev200 which handles an area >2700ft2.
.
Sounds like you are living the home currently. I would size the ERV on the need for fresh air. All homes have a natural leakage rate. Most homes leak enough air during cold weather to not require supplemental fresh air. The sign of inadequate winter fresh air is dripping moisture on windows during cold weather. <.5 " of moisture on the bottom of a window during the 1st cold snap is ok. Also avoid deep t-stat set-back, keeping the window warm during cold evenings. Any of these excess moisture signs indicates moisture sources inside the home or a need for year around additional fresh air ventilation.
Severe window condensation suggest 100 cfm of fresh dry air ventilation. Using an ERV which returns about half of the exhaust air humidity, requires double the volume of fresh air for the same amount of moisture removal.
Moderate condensation suggest 50-75 cfm of additional make-up fresh air ventilation. This could achieved by operating a bath fan on a daily routine.

After getting enough fresh air to keep the window from dripping, maintain the same ventilation when the windows are closed through the summer. In green grass climates, maintain <50%RH (summer) to avoid mold/dust mites and provide comfort.
Regards, TB

[montr]

I stumbled across this forum 3 days ago. It has exactly the info I've been wondering about.

I also live in SE Wisconsin and am planning on installing a renewaire erv. My question is sizing the erv. I have a house with a vaulted ceiling and walkout finished basement.

The upper level of the house 2400 ft2. The basement heating and cooling is not optimal as there are only two heat vents, no returns. Assuming I will not change anything in the basement regarding forced air heat, do I size the erv for the 2400 ft2 upstairs or do I include the basement too?

the units I am looking at are the ev130 (handles 2700 ft2) or the ev200 which handles an area >2700ft2.

side note: the ev200 seems a bit more energy efficient, but I don't really understand the numbers... http://www.renewaire.com/for_your_home/what_product_fits_you.php

thanks in advance.


I think the recommendation for sizing are based on about a total air volume change every 3 hours. I have 4000 sq ft and I got a EV200. The limit of 2700 sq ft for the EV130 is for 100% run time. If you get the EV200 (which is more efficient), you can get the same result as a EV130 by running 65% of the time. You can do this by using a ERV controller (RenewAire has one, I used AirCycler instead).

[emcoasthvacr]

For your conditions, the ERV is better suited since it provides better moisture control and enthalpy(energy) transfer.

Both ERV & HRV utilize bypass dampers and wheel speed control, but the ERV spanks the HRV's butt when it comes to latent energy effectiveness (ERV & HRV have similar sensible energy effectiveness).

You alluded to the Carrier unit sounding like both an HRV & ERV. Some units use a Precooling Air Reheater that utilizes humid outside air, which is precooled through the exchanger and subsequently passes through the cooling coil. Then, the cooled dehumidified air is reheated by passing through the other side of the exchanger, reheating the supply air -- I suspect the Carrier unit does this.

[Carnak]

In the winter, the ERV has the advantage over the HRV in that it will not over dry the house if the steady constant supply of fresh air is desired.

In the summer the ERV CAN be installed to greatly reduce the latent load of the fresh air you are supplying to the home.

[teddy bear]

I think the recommendation for sizing are based on about a total air volume change every 3 hours. I have 4000 sq ft and I got a EV200. The limit of 2700 sq ft for the EV130 is for 100% run time. If you get the EV200 (which is more efficient), you can get the same result as a EV130 by running 65% of the time. You can do this by using a ERV controller (RenewAire has one, I used AirCycler instead).

All homes have a natural leakage rate from wind and stack effect. The amount of leakage is varible and depends on outside/inside tempature differential and the volcity of the wind. Most homes leak enough fresh air during the winter weather to approach the 200 cfm of fresh air. This makes the home very dry and may require humidification. The tightest of home are 50-75 cfm of natural. Add in the effect of clothes drier, kitchen hood, bath fans, and gas water heater for the total the air change effect. Operating balanced flow ERV/HRV adds to the natural ventilation of the home. Sizing ventilation should consider natural leakage of the home and the number of occupants more the total sqft. of the home. Adding 100 cfm of balanced fresh air ventilation to home to the best of homes means +150 cfm. The time of year that natural ventilation is the lowest is spring/summer/fall during low wind. Under this condition, 50-100 cfm fresh air is adequate to purge pollutants and renew oxygen. A sign of inadequate fresh air is sweaty windows during cold weather. During winter, adding ventilation to home with dry windows may not be necesary. Most homes would benefit from fresh during the rest of the year. In green grass climates, warm weather ventilation has a moisture load. Maintaining <50%RH is critical to avoid mold and dust mites. 100 cfm of 70^F dew point outside fresh air in through a 50% effecient ERV is 2 lbs. of moisture per hour added to the home. When the clothes drier is operating, 150 cfm or 6 lbs. moisture per hour. Each adult is .25 Lbs. per hour. A 2,500 sqft. basement maybe 1-2 lbs. per hour. An a/c operating at full cooling load will remove all this moisture and maintain <50%RH. With rainy weather and no a/c cooling load, 70-100 pints/day of dehumidifcation is required to maintain <50%RH. If 200 cfm is the amount of fresh air ventilation, up the dehu capacity to 150 lbs. per day.
ASHRAE recommends 7.5 cfm per adult + .01 cfm per sqft. + natural ventilation as a starter. Regards Dehu TB.

[Carnak]

Tight home is in the eye of the beholder teddy.

Many are significantly lower than the natural rate of 50 to 75 CFM.

And when you run a one sided ventilation scheme, by pressurizing and exhausting, you already know that the natural infiltration goes out of the equation.

In a cold climate, after the water of new construction was gone, such as the second winter an HRV even on low speed like 75 CFM, combined with the natural infiltration will overdry a house and people will be tempted to install humidifiers. The ERV has an advantage here.

An HRV, capable of moving a higher volume of air at about 0.3 airchanges an hour can function intermittenrtly on a rise in humidity and keep those windows clear. As indoor humidity rises so does CO2, so indirectly the CO2 is being controlled in the winter time.

The ASHRAE ventialtion rates also assume so much infiltration occuring in the space, perhaps 2 CFm for every 100 square feet. This was in the back of their minds when they came up with some many CFM per person and so much ventilation CFM per square foot.

With one sided ventilation this is gone in the tighter homes.It may very well take a steady 50 to 75 or more CFM on the one sided systems to provide the IAQ because the infiltration has been eliminated.

[chinahvacboy]

In the winter, the ERV has the advantage over the HRV in that it will not over dry the house if the steady constant supply of fresh air is desired.

In the summer the ERV CAN be installed to greatly reduce the latent load of the fresh air you are supplying to the home.

yes.I have the same opinion

[Carnak]

It's a fact, jack :)

[Cory Fowler]

Evening to everyone.

I have read some of the statements below which are helpful. I ask anyone that has direct working with these devices to please sound out I need all the information that I can gather about these devices. I am in the second year of the HVAC degree from the local college and we are wrapping up the psychrometric charts and starting into the fresh air input and how it affects the pocket book of the home owner and the beneficial effect concerning health.

Thank You

[Cory Fowler]

Thank you for the informative articles that I have read! Hands on education is still number one in my book. I have been in the copper tubing manifold and tube and fin coil business for 24 years and due to my plant getting move to Mexico I am now getting into the HVAC field and this information is great guys thanks!

[sancyk]

First, just about all of the HRV's and ERV's distributed in North America are built either by Venmar or Lifebreath. Companies like Bryant, Lennox, Broan, Carrier, etc. just rebadge these manufacturers' boxes.

Too funny.

According to hvi.org, all of these units have the same specs:

Bryant ERVBBLHU1150
Carrier ERVCCLHU1150
Frigidaire ERV 150
Maytag ERV 150
Partner's Choice ERV-150
Rheem 84-ERV-100
Ruud 84-ERV-100
Tappan ERV-150
Westinghouse ERV-150

Is this a good ERV. Which is better, this one or the vanEE 1001 ERV (Broan ERV100HC)

[DanW13]

I stumbled across this forum 3 days ago. It has exactly the info I've been wondering about.

I also live in SE Wisconsin and am planning on installing a renewaire erv. My question is sizing the erv. I have a house with a vaulted ceiling and walkout finished basement.

The upper level of the house 2400 ft2. The basement heating and cooling is not optimal as there are only two heat vents, no returns. Assuming I will not change anything in the basement regarding forced air heat, do I size the erv for the 2400 ft2 upstairs or do I include the basement too?

the units I am looking at are the ev130 (handles 2700 ft2) or the ev200 which handles an area >2700ft2.

side note: the ev200 seems a bit more energy efficient, but I don't really understand the numbers... http://www.renewaire.com/for_your_home/what_product_fits_you.php

thanks in advance.

Have you called to talk to the people at Renewaire, if not give them a call and talk to Duane hes a pretty nice guy and will answer all your questions, I just purchased there EV-130 have not had the unit installed yet but will have with in the next week, I'm also in WI, up in Sheboygan, I'm going with a dedicated duct system to include the baths and living spaces with individual exhaust points and dump the fresh air into my return air to the furnace. Get the percentage run timer and if need be get a 2nd or 3rd point of use for the bath ares if needed for showering to run and exhaust the excessive moisture. If you haven't already purchase the Renewire give me your e-mail I got a place where you can buy them fro a very good price !!