Lots of questions about HVAC

[csimpson]

My house will be 1915 sqft living
It is two story with about 900 of the total sqft on the second story.
I will be using Icynene foam insulation and I plan on doing the total encapsulation thing.

I am building in southeast Louisiana. I have heard I should get a heat pump from some, I have heard I should get an air conditioner and a gas furnace from others, and I have heard the I should just get air conditioning with an electric heater from yet other people. Seems most of the information on heating is for up north, so I am pretty confused which is the best for my climate.

How important is an ERV for for the type of construction I have described?

I have mentioned make-up air to every HVAC guy I talked to and they all acted like I was from Mars. At what point should I need to worry about make-up air when looking at my kitchen & bath ventalion?

Most people around here HVAC guys included say I should get two units because zoning doesn't work well in this climate. Is this true? Or is it posible I haven't met anybody that knows anything about it?

Last question. Is the brand of equipment really important? Is there any real difference from the big three Trane, Carrier, and Lennox compared to stuff like Philco, Goodman, or Rudd other than the price?

[pstu]

I am a homeowner in S.Texas, if your house is as airtight as I expect it will be, you will need some form of mechanical ventilation. Let me suggest a ventilating whole-house dehumidifier, because you will have humidity issues even when there is no need for cooling. I am eager to hear debate from pros, believe an ERV is good for ventilation but about 80% placebo when it comes to effective control of either heat or humidity. In climates like yours and mine.

This isn't an answer to all your questions but is a start.

Best of luck -- Pstu

[csimpson]

Is ventilating whole-house dehumidifier in addition to or instead of a ERV. Also does anyone have any input on my other questions? Thanks in advance.

[pstu]

If you are made of money, IMO the ideal equipment would be an ERV plus a ventilating dehu. I usually assume the homeowner has only enough funds to choose between one and the other. Under limited funds I vote strongly for the dehu first. I also wish we would hear from some of the pros on these questions!

Best wishes -- Pstu

[BaldLoonie]

Friend of mine is a foamer. He refers people to www.energywisestructures.com for equipment sizing. Too many HVAC dealers want to oversize with foam, they don't realize how tight it is.

Let's see if Teddy Bear sees this. I think Thermastor has a whole house dehum with outdoor air capability to keep the place dry and provide dry fresh air.

[dan sw fl]

My house will be 1915 sqft living
It is two story with about 900 of the total sqft on the second story.
I will be using Icynene foam insulation and I plan on doing the total encapsulation thing.

I am building in southeast Louisiana. I have heard I should get a heat pump from some, I have heard I should get an air conditioner and a gas furnace from others, and I have heard the I should just get air conditioning with an electric heater from yet other people. Seems most of the information on heating is for up north, so I am pretty confused which is the best for my climate.

1. How important is an ERV for for the type of construction I have described?

2. I have mentioned make-up air to every HVAC guy I talked to and they all acted like I was from Mars. At what point should I need to worry about make-up air when looking at my kitchen & bath ventalion?

3. Most people around here HVAC guys included say I should get two units because zoning doesn't work well in this climate. Is this true? Or is it posible I haven't met anybody that knows anything about it?

4. Last question. Is the brand of equipment really important? Is there any real difference from the big three Trane, Carrier, and Lennox compared to stuff like Philco, Goodman, or Rudd other than the price?

1. With very limited O.A. make-up, an ERV would not be a great energy saver.
2. Make up air should be ~60 CFM
3. Use 2 stage heat pump, Variable Speed air handler and zoning
4. 10 year Parts & Labor Warranty is a small upcharge for higher SEER equipment.

[cem-bsee]

get a lot with large trees!
do not let the builder cut them down!
put house on NE side of trees -- better yet, have trees on east, west & south, no windows on west [put the gar there]

put on sticky underlayment on roof
read at StrongTie about gar door framing

get a good HVAC contractor -- MUCH more important than brand of unit!

there has been lots of discussion about building in humid wet areas herein --
read at BUILDINGSCIENCE.com

[csimpson]

1. With very limited O.A. make-up, an ERV would not be a great energy saver.
2. Make up air should be ~60 CFM
3. Use 2 stage heat pump, Variable Speed air handler and zoning
4. 10 year Parts & Labor Warranty is a small upcharge for higher SEER equipment.

Let us say I had a kitchen hood that was somewhere between 300 and 600 cfms. Would an ERV produce an energy savings while at the same time providing make-up air for the hood, or is this something that someone would need a specially designed make-up air system just for the kitchen hood.

Also every bid I have gotten so far includes an electric heater whether the bid is just for AC or a heat pump. So, I guess my question is when does the heat pump actually help heat the house, or is it possible I am I getting bad info from unknowledgeable HVAC contractors?

On the higher SEER equipment it looks like there are two types of refrigerant, which one should I choose in building a new house and why? Also I notice there are different types of compressors, scroll for instance. Is one better than the other?

[CottyGee]

LOL - a couple of the 64 thousand dollar questions!

I'm just a homeowner and have been "studying" here for several weeks. I asked a couple of the same questions and my conclusions are scroll compressors with R410a refrigerant. There are Pros that will argue both sides of both questions, but if you're planning on being there for the expected life of the equipment (ballpark at least 15 years) then the new refrigerant maybe makes sense. In reality, it probably doesn't matter tho.

Heatpumps do heat houses! I have no idea what your climate is like and how well heatpumps do. But in Phoenix where the lowest of the low temps we EVER see are in the mid- to high-20ºF range, they work just fine.

[Shophound]

Let us say I had a kitchen hood that was somewhere between 300 and 600 cfms. Would an ERV produce an energy savings while at the same time providing make-up air for the hood, or is this something that someone would need a specially designed make-up air system just for the kitchen hood.

Also every bid I have gotten so far includes an electric heater whether the bid is just for AC or a heat pump. So, I guess my question is when does the heat pump actually help heat the house, or is it possible I am I getting bad info from unknowledgeable HVAC contractors?

On the higher SEER equipment it looks like there are two types of refrigerant, which one should I choose in building a new house and why? Also I notice there are different types of compressors, scroll for instance. Is one better than the other?

600 cfms for kitchen exhaust? At that rate you'd be better off with make-up air piped directly to the kitchen from outdoors via a dedicated make-up system for the kitchen vs. using a whole-house method for make-up air. That's a considerable amount of air...is it one of those commercial hoods? For a house just under 2000 square feet, a 600 cfm exhaust hood could easily de-condition the air in your house if the make-up air is not filtered and conditioned. I'd look for a much smaller cfm range for a kitchen hood...typically around 100 cfm.

If you are planning to build a tight house, you will need make-up air. Using foam for insulation will yield you a considerably higher R value in walls and ceilings vs. fiberglass batts, and the infiltration rate will be a lot lower, being that foam seals well. Since you are in Louisiana I'd give whole house dehumidifiiers with outside air make-up a serious look. Teddy Bear is our resident dehum expert...hope he weighs in on this one.

Heat pumps use electric strips for more than one purpose. Not only for supplemental heating when outdoor temperatures are quite low, but also so you don't get chilled when the heat pump must defrost its outdoor coil. With a tight, well insulated house in your location, I don't see the auxiliary heat running all that much, but you will want heat for when the system must defrost itself.

[dan sw fl]

1. Let us say I had a kitchen hood that was somewhere between 300 and 600 cfms. Would an ERV produce an energy savings while at the same time providing make-up air for the hood, or is this something that someone would need a specially designed make-up air system just for the kitchen hood.

2. Also every bid I have gotten so far includes an electric heater whether the bid is just for AC or a heat pump. So, I guess my question is when does the heat pump actually help heat the house, or is it possible I am I getting bad info from unknowledgeable HVAC contractors?

3. On the higher SEER equipment it looks like there are two types of refrigerant, which one should I choose in building a new house and why?
Also I notice there are different types of compressors, scroll for instance. Is one better than the other?

1. Kitchen hood air laden with even small amounts of grease and moisture would make an ERV nearly useless in a very short period.

O.A. recommended is very little ( ~ 5%) in comparison to air handler flow rate.

2. Electric strips are used as auxiliary at lower ( say < 28' F, dependent on house and heat pump sizing) temperatures when the house heating requirements are increased and the heat pump output/efficiency is reduced.

3. R-410A is the refrigerant of the future at-this-time.
R-22 is being phased out and will only be available in new equipment for 2+ years (Jan. 1, 2010).

http://www.epa.gov/ozone/title6/phaseout/22phaseout.html

Write me an e-mail if you need specific residential HVAC, O.A. or energy cost guidance for your house & locale.

Your energy requirements will be significantly (~20% ... spray foam) reduced with the use of zoning, spray foam and proper duct design.

[teddy bear]

Is ventilating whole-house dehumidifier in addition to or instead of a ERV. Also does anyone have any input on my other questions? Thanks in advance.
With your need for make-up air for bath fans, clothes drier, and kitchen hood, suggest the whole house ventilating dehumidifier. You need enough make-up air to purge the indoor pollutants and renew the oxygen. Bath fans exhaust 50-80 cfm. Clothes driers are 80-120 cfm. Ultra-Air dehu is avialable with timer to schedule 60-100 cfm during routine occupancy. This is also the time that the bathfans/drier maybe operating. In addition the UA has a merv 11 air filter for the fresh and house air. Humidity control is adjustable and usually with a <50%RH setting. Proper ventilation requires supplemental dehumidification for the rainy wet times of the year with low/no cooling load.


Let us say I had a kitchen hood that was somewhere between 300 and 600 cfms. Would an ERV produce an energy savings while at the same time providing make-up air for the hood, or is this something that someone would need a specially designed make-up air system just for the kitchen hood.
?

An ERV is a balance flow device that exhaust stale air and introduces fresh air at the same time transfering a portion of heat and moisture from hot/wet to cool/dry stream. In your moderate climate, the savings are minimal. They do not provide make-up air. Dealing with a large exhaust hoods is mater of saftey. If the hood is operated on high flow for extended periods, providing make-up can be provide with a seperate make-up system or a dampered adequate make-up air on the return of the a/c air handler. If only operated occasionally, opening a ajouning screened window for make-up air may be an alternative. An open fireplace or water heater may backdraft when the kitchen hood is operated on high. Maybe a large hood with 150 cfm max flow is a better alternative. Dehu TB

[csimpson]

With your need for make-up air for bath fans, clothes drier, and kitchen hood, suggest the whole house ventilating dehumidifier. You need enough make-up air to purge the indoor pollutants and renew the oxygen. Bath fans exhaust 50-80 cfm. Clothes driers are 80-120 cfm. Ultra-Air dehu is avialable with timer to schedule 60-100 cfm during routine occupancy. This is also the time that the bathfans/drier maybe operating. In addition the UA has a merv 11 air filter for the fresh and house air. Humidity control is adjustable and usually with a <50%RH setting. Proper ventilation requires supplemental dehumidification for the rainy wet times of the year with low/no cooling load.

I am planning to talk to a Lennox installer in my area as soon as find time. Would their Ventilation Control System http://www.lennox.com/products/overview.asp?model=LVCS in conjuction with their Humiditrol® Whole-Home Dehumidification System http://www.lennox.com/products/overview.asp?model=HD be the same thing, or similar to what you are referring to? Or is the Ultra-Aire product something completely different?

[teddy bear]

I am planning to talk to a Lennox installer in my area as soon as find time. Would their Ventilation Control System http://www.lennox.com/products/overview.asp?model=LVCS in conjuction with their Humiditrol® Whole-Home Dehumidification System http://www.lennox.com/products/overview.asp?model=HD be the same thing, or similar to what you are referring to? Or is the Ultra-Aire product something completely different?

This lennox reheat equipment looks better than conventional a/c. According to a Lennox contract's feedback, Humiditrol needs +80^F to provide humidity control without over-cooling. You get <2 pints per KW with Humiditrol. You must operate the a/c air handler to suck in the fresh air.
Ultra-Aire is a ventilating whole house dehumdifier. Air handler operation is not required while ventilating. UA removes 5 pints per KW. UA will not overcool your home.
Lennox ventilation control avoids ventilation if humid or cold outside. Fresh air ventilation is necessay when the home is occupied. The cost of conditioning the fresh air for 10 hours/day is <$200 for the entire year. Neglecting fresh air for a day, week, or months is not the ideal way to provide IAQ. The cost of the equipment is similar. UA is simpler dedicated ventilation/humidity control unit connect to the a/c ducts. Lennox contractors are able to purchase UA through Lennox distribution. Dehu TB

[csimpson]

Thank you for all the information about dehumidification and ventilation.

Why is zonning supposed to better than a seperate sytem for each floor? And what questions should I ask an installer to verify that he does know the proper way to set-up a zoned system? Is there certain things that I should make sure are done on a zoned system to ensure that it will work properly?

Is a two-stage heat pump and variable speed blower worth the additional cost if you have a seperate dehumidification system? If yes why? I thought the whole reason for the variable speed blower and the two-stage heat pump was for humidity control. Am I wrong about this?

[dan sw fl]

Is a two-stage heat pump and variable speed blower worth the additional cost if you have a seperate dehumidification system? If yes why? I thought the whole reason for the variable speed blower and the two-stage heat pump was for humidity control.

A more valid question and outlook should be ...
Is a seperate dehumidification system worth the additional cost
if you have 2-stage Heat Pump and Variable Speed blower?

What are the installation and operating cost benefits?

[pstu]

Are you looking to optimize cost, or to optimize comfort?
What level of humidity do you find acceptable in your house?
Are you willing to use the air conditioner to remove humidity, when cooling is not needed?

The answers to the above would shed a lot of light on what equipment is the best buy. For myself, I find there are a lot of cool but humid days in spring and fall, and there is no way to get 45&#37; RH in the house without a dehumidifier. My situation is such that I want a VS furnace and enhanced dehumidification via the AC as well. So I guess I am ordering the whole menu. Another customer might go to extremes in the other direction, such as just opening the windows and let the humidity go where it will. They would say that is most economical of all.

Hope this helps -- Pstu

[cem-bsee]

it is interesting that Lennox does not ventilate if humid or cold!
just what is recommended for a system, say in Huntsville AL?
[where our outdoor RH is high yr around!]

[csimpson]

A more valid question and outlook should be ...
Is a seperate dehumidification system worth the additional cost
if you have 2-stage Heat Pump and Variable Speed blower?

What are the installation and operating cost benefits?
That is a good point.
So, which of these two systems will perform better at keeping humidity in check, which one would likely be cheaper to purchase initially, and which one would be cheaper to run long term?

1.) Two-stage heat pump with variable speed blower and some type of outside ventilation, whether that be an ERV or a hole in the wall with air being piped into the return duct.
In most cases the two-stage heat pump would put you around 16 seers or better.
2.) Heat pump approximately 15 seers and a non-variable speed blower with something along the lines of Ultra-Aire whole house ventilating dehumidifier.



Are you looking to optimize cost, or to optimize comfort?
What level of humidity do you find acceptable in your house?
Are you willing to use the air conditioner to remove humidity, when cooling is not needed?

The answers to the above would shed a lot of light on what equipment is the best buy. For myself, I find there are a lot of cool but humid days in spring and fall, and there is no way to get 45% RH in the house without a dehumidifier. My situation is such that I want a VS furnace and enhanced dehumidification via the AC as well. So I guess I am ordering the whole menu. Another customer might go to extremes in the other direction, such as just opening the windows and let the humidity go where it will. They would say that is most economical of all.

It is difficult to say what is more important to me I guess it is more of a balance. Obviously I don’t want a system that is not going to keep humidity in check. But I also don’t want to pay for more HVAC equipment than I need. I pretty much know nothing about this subject. I have heard information from various people who I think know about as much as I do about HVAC equipment. My only reason for posting here is I am just trying to learn as much as I can so I can make the most inform decision I could make when that time comes in the coming months ahead.

For example the zoning questions I asked in my previous post; everyone tells me that I don’t want to zone. They all say I want two separate systems; however, everything I read on the internet says to zone a two-story house. The only problem is I don’t know why that is supposed to be better, so when the HVAC installer asked why do you want to do a zoned system I just go, “Ummm, because the internet says so?”. Now I instantly look like someone that know nothing and is primed to be taken advantage of.

I just want to know what I should be asking for and the reasons behind it.

[pstu]

If you are not keeping humidity levels pretty much in mind, I believe you will be happy enough with just an AC system which does a good job at dehumidifying. I suggest you add to your list of options... a single stage AC coupled with a VS blower (and of course a TXV). That would let you shop for as little as 12 SEER or as high as 16 -- e.g. the Trane XL15 is capable of 16 SEER with many coils. You can have it set up for lower airspeed upon startup, then ramping up to full speed after several minutes. Trane calls that system "Comfort-R" and claims 40&#37; better humidity removal. This is not unique to Trane, most any maker should offer something like that.

This is something you can do even without 2-stage equipment, and save some money. As I see it the one unique benefit of 2-stage AC is long runtimes at 1st stage which is supposed to deliver better comfort -- you can probably use your imagination to estimate whether there is any comfort shortcoming with your present single stage AC. FWIW I am going for that myself with a 2-stage system being installed *today*.

You can also include a humidistat which will lower air flow when humidity removal is needed, trading off sensible cooling (thermometer) for better latent cooling (humidity removal). This is an option whether 1-stage or 2-stage AC.

My own opinion is rather hawkish on having low humidity, but not everyone needs to share this opinion. I am an AC nerd but my wife is not, she endorses the comfort benefits of the dehumidifier for what that's worth. However if you keep relative humidity (RH) under 60% then many would say you are acceptable and will avoid any mold tendencies. People generally agree comfort improves as you go down to 50%, many AC systems can maintain 55% fairly easily in cooling season. The "problem" of mild humid weather I refer to is something not everybody agrees is worth the investment. That is more of a luxury option for many people.

Based on all this background, I will retract my idea that you might *need* a dehu to feel fully comfortable. Some people do, some don't, if you do then you will figure out this subjective decision for yourself sooner or later.

One last thing, most everybody agrees you will feel cooler in a house with lower humidity, so if you are running at 50% RH rather than 60% you can usually set the thermostat higher with equal comfort. A bit of energy savings there but not a great amount.

Hope this helps -- Pstu

[dan sw fl]

That is a good point.

So, which of these two systems will perform better at keeping humidity in check, which one would likely be cheaper to purchase initially, and which one would be cheaper to run long term?

1.) Two-stage heat pump with variable speed blower and some type of outside ventilation, whether that be an ERV or a hole in the wall with air being piped into the return duct.

In most cases the two-stage heat pump would put you around 16 seers or better.

I just want to know what I should be asking for and the reasons behind it.

Are you willing to use the air conditioner to remove humidity,
when cooling is not required?

I believe that many (most) people would not select A/C to be ON
when temperature is < 78'F and dew point is < 62'F { < 65&#37; R.H.).
77' F DB / 64'F WB / 61'F DewPt / 58% R.H. / W 81 grains per lb /
Enthalpy 31.2 BTU per lb

Use of humidity control may be selected when outside conditions are: Dew Point is > 62'F and Temperature is < 78'F.
For example, 77'F DB/ 68' WB/ 64'F Dew Point / 65% R.H./ W 89 Grains per lb/ Enthalpy 32.5 BTU per lb

At > 80'F your A/C will run a considerable amount of time providing humidity control
and a dehumidifier set to the low 50's% range would have very limited run time.

Installation co$t is the determining factor the majority of the time.
Have you determined an approximate HVAC budget?
Dehumidifier set-up is not cheap. A 4-zone system with one heat pump is less cost than two systems.

Only select a Mechanical Contractor who has significant experience with zoning.

A simple 4-zone system for your 1,915 S.F. 2 story might be :
http://www.zonexsystems.com/digi4/digi.htm

Add your e-mail address in your profile for more detailed weather data
and other more specific info on zoning and sizing.

The amount of time and the time periods that your locale experiences this condition are critical to Your Comfort. Obviously, mild temp with moderate to high humidity condition will be present mostly in the shoulder seasons (April/May, Sept/Oct) and summer nights. However, with 2-stage heat pump and programmable thermostat, I believe that your environment would be well controlled and exceed your comfort requirements.

[teddy bear]

Well installed RVs cost as much as whole house ventilating dehumidifiers. Vent dehus provide make-up air for other appliances.
Most evenings outside is near 100%RH, hence dew on grass with little a/c load. Most rainy days are <80^F. During rainy weather, a/c loads are low or none.
A/c's ability to control humidity is dependent on occasional rainy weather. During dry weather works fine. During extended wet cool weather with adequate fresh air ventilation, you will have a damp house.
The dehu provides excellent humidity control without any a/c operation and fresh ventilation. A/c must remove 3X more sensible heat than latent heat(moisture). During wet weather with fresh air ventilation and people, 90 lbs./8 gal./100,000 btus of latent-(moisture) must be removed from the home to maintain <50%RH.
So during dry hot weather or occasional rain, no problem with a/c only. But during wet cool weather, a serious problem could result. You can add the dehumidifier after the problem occurs. That's what most of dehu users did. Keep us posted. Dehu TB