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We ran a blower door test and did some infra red camera snooping yesterday.

The house has a leakage rate of 0.215 volumes at 50 Pascals. It has an equivalent open area of 172 square inches. Given the size of the house, this is considered very good.

Infra red testing showed everything to be really good with the exception of pot lights in the upper floor, a leak in the attic entrance area and a leak where the gas line enters the house. Tightening up these areas will further reduce the air leakage rate.

The tester strongly agreed that a house this big and this tight needs an active ventilation system.

There is no way a seasoned or as you put it a journeyman hvac specialist can tell how tight your house is without a blower door test done to CFM50 standards..

I have seen foamed insulated houses that are supposed to be airtight to the point of needing ventilation added that were as leaky or more so as a conventional home.

TB is correct if you have humidity issues with two operating humidifiers then you have serious air leakage or your leaving a window or door open..

This leakage could be caused by ducts leaking outside the envelope, supply ducts in attics are a major problem if leaky as the air that is leaked outside must be replaced by that dry outdoor air that is outside..

Get a blower door test performed to CFM50 standards and find your problem.. Your bills may be reduced, your comfort will be increased and your humidity level issues will go away...

Look for a company that is BPI certified or comfort institute certified..

Goodluck
J

The home is airtight. We found a "fanless" heat exchanger hidden in the ducting allowing 150CFM or more into the house. Thus the low humidity.

The fanless heat exchanger isn't high quality. I'm replacing it with the fanned HRVs.

Standard minimum air exchange in a home is 1/3 volume per hour. The house is 37 x 52 x 3 floors x 9 foot ceilings. 52,000 ft^3. 52,000 x 0.3333 / 60 = 288 CFM. If you have less than that much air moving through the house, its going to be stuffy. We live in a house like that right now. No thanks.

The other thing I'm learning is that humidifiers effectively put out way less moisture than they are rated for. If both of the humidifiers in that house were putting out 18 gallons a day, there wouldn't be a low humidity problem.

Nobody talks about this, but the moisture uptake with cold water into a cold plenum is poor. In a tight, well insulated house running heat exchangers, the furnace doesn't run much. Even if the humidifiers are wired to demand the blower, the air in the plenum is 70F and not much gets absorbed. For maximum evaporation, the water going to the humidifiers should be hot, 140F. That will also cut down a bit on the chilling effect of adding the moisture.

Another issue is contamination of the evaporation pads with minerals. Calgary has hard water. I'm installing a water softener for this and other reasons.

Steam is the ultimate answer here, but its expensive to run when the boilers are electric. That is why I'll use evaps for the base load and steam for supplementation.

I'll probably also add a small duct fan to the bypass piping on the 600s to ensure lots of air flow through them. We are going to install them first and see how they run without.

Originally Posted by BigBear23

I had a journeyman HVAC specialist in the house yesterday. He said its "as tight as a drum" leak wise. In his opinion a blower door test isn't needed.

We inspected the existing Honeywell humidifiers. Both are set at 100% humidity and in good order. The house is extremely dry.

You have to remember that the outdoor humidity in Calgary can be as low as 10% when a Chinook is rolling through. These are extreme conditions.

We reviewed my plan to install AA600s for base duty and AA800s for the extreme conditions and he agreed it was a good way to handle the situation.

He calculated the minimum necessary ventilation rate for the house and came up with 280 CFM. Thus he agrees with my desire to install 2 150 CFM HRVs.

Only in Canada! Two humidifiers going 24/7. The home is too air tight. There something wrong with this picture. This will be another learning experience, may be a little expensive.
If your humidifiers are working and the home is very air tight, the windows should be condensing moisture during cold evenings.
Get some help from someone who knows building science principles and not selling something.

If your humidifiers are adding 2-3 lbs of moisture per hour and your home is <30%RH at 68^F, you have +150 cfm of fresh dry air infiltration passing through your home. If drier, you have more fresh air infiltrating your home. 280 cfm of ventilation is more fresh air than your home needs.
The HRVs will make your home much driers than it is now!! With all of the proposed changes, you will need 10 lbs. of moisture to humidify the space. This is 10,000 btus of evaporation heat per hour!!
Keep us posted on how this all works.
Regards TB

I had a journeyman HVAC specialist in the house yesterday. He said its "as tight as a drum" leak wise. In his opinion a blower door test isn't needed.

We inspected the existing Honeywell humidifiers. Both are set at 100% humidity and in good order. The house is extremely dry.

You have to remember that the outdoor humidity in Calgary can be as low as 10% when a Chinook is rolling through. These are extreme conditions.

We reviewed my plan to install AA600s for base duty and AA800s for the extreme conditions and he agreed it was a good way to handle the situation.

He calculated the minimum necessary ventilation rate for the house and came up with 280 CFM. Thus he agrees with my desire to install 2 150 CFM HRVs.

Originally Posted by BigBear23

Thanks for the advice, TB.

I don't think there is any way that these homes (current one and the one we are moving into) have 150 CFM of fresh air infaltration. They are built way too tight.

I am thinking of putting a VHR unit in the new house. It has 2 air returns, 1 per heat exchanger. Should I put 1 or 2 VHRs in and how big should I make them ?

Adding 3 lbs of moisture per hour to a home that has 150 cfm of infiltration will raise the indoor dew point 23^F. With a 12^F outdoor dew point, the indoor humidity will be 30%RH at 68^F and 30^F dew point. Try adding a specific amount of moisture to the home for a couple days. The rise of the inside %RH after a couple of weeks determines amount of air passing through the home. This is basic science. If you are right about not enough fresh air, the windows will drip with moisture. A single person adds .5 lbs. of moisture per from breathing and activities.
If you have unlimited funds, get a HRV, a couple of steam humidifiers, and a whole house dehumidifier for the times with the outdoor dew points are +60^F. Than you can have 30%RH during cold weather and <50%RH during the mild months of the year.
6 occupants 24/7 would provide 30%RH to a home that has 150 cfm of infiltration and a 12^F outdoor dew point. If you have less occupants and/or less hours, add moisture from a humidifier. Short term, you can boil water on the stove to determine the amount of infiltration.
Regards TB

Thanks for the advice, TB.

Originally Posted by teddy bear

You will need 3-4 lbs. per hour of moisture to humidifier 150 cfm of fresh air that infiltrates a 5,000 sqft. home.

I don't think there is any way that these homes (current one and the one we are moving into) have 150 CFM of fresh air infaltration. They are built way too tight.

I am thinking of putting a VHR unit in the new house. It has 2 air returns, 1 per heat exchanger. Should I put 1 or 2 VHRs in and how big should I make them ?

I would make sure your humidifiers are operating 24/7 before replace good equipment. You will need 3-4 lbs. per hour of moisture to humidifier 150 cfm of fresh air that infiltrates a 5,000 sqft. home. Get your current humidifiers operating agood as possible. Avoid electric humidifiers because of cost of operation and maintaince. Get more air flow through your humidifiers.
Regards TB

I think I'm going to install an AprilAire 700 in each of the heat exchangers for the "normal" humidifying load and back them up with an AprilAire 800 downstream in the duct as needed.

I'll run separate humistats on each. I'll have the 700s kick in first and only fire up the 800s if/when needed. Maybe have the 700s kick in at 40%rh and the 800s kick in at 30%rh. Something like that. I should then have more than enough capacity for all conditions.

It sounds like a lot of hardware, but it isn't going to take long to pay for the 700s (at $230 each) with the 800s costing 25 cents per hour each to run. They should pay for themselves in a single season (1000 hours). I can buy a AA700 and an AA800 for the price of a single General Air steam unit.

I like fan evaporative units over bypass units because their performance is independent of ducting pressure differentials.

I'm going to pipe hot water into the 700s to increase their effectiveness.

Originally Posted by BigBear23

A blower door test is an excellent idea. I'm waiting for call backs from 2 such service providers.

Lets assume these houses are pretty decent leak wise. Given the natural gas bill for the house I'm currently in, I believe that to be the case. If it is, what would you use to humidify the house ?

I think you mentioned elsewhere that there is a large outside make-up air duct to the furnace - it sounds like that is bringing in too much air for the humidifier to make up for. IT sounds like some air balance adjustments may be necessary. Either way, your existing humidifiers should be plenty large enough (one of those is likely rated for up to a 4000sq ft house, if done right).

Originally Posted by CraziFuzzy

This response is going to cross over to your other post regarding fresh air change. If two of those honeywell drum humidifier aren't keeping up, then the house is very leaky. I'd say in this case, your first step would be to have a blower-door test done on the home, and find the major leak points, and tighten up the envelope. Of course, if you get it too tight, you will then have to look into the fresh air exchange, but it will be well worth it in the end. Either way, it seems both questions being asked are pointing to the same first step.

A blower door test is an excellent idea. I'm waiting for call backs from 2 such service providers.

Lets assume these houses are pretty decent leak wise. Given the natural gas bill for the house I'm currently in, I believe that to be the case. If it is, what would you use to humidify the house ?

Originally Posted by CraziFuzzy

I wouldn't base the humidifier choice on the controller - in most cases, you'd be better off replacing the main thermostat with one that controls humidity as well, so it is all controlled as a single system.

That is a very interesting idea. The new house is getting a Zwave automation upgrade, including the thermostats. It probably wouldn't be too hard to integrate control of the humidifiers into the system.

For starters, you may NOT want the humdifier running unless the heater is also running, simply because you end up getting 'cool' air blowing out the vents when this is happening (it is essentially an evaporative cooler).

That is a very good point. Now that you say that, we sometimes find the house to be cold when the thermostat is set to a reasonable temperature and then find it too warm at the same temp a while later.

How would the cooling effect change if steam was injected into the air flow rather than evaporated water ? The air would be moist and warm or at least not cold ?

Really, the only good way to coordinate this is with a singular controller for both temp and humidity. Most that support this also support an outside temp sensor, to prevent dew formation on the windows.

This is an incredible forum. This is the first that I have ever heard of that type of controller. Can you recommend a brand or model ?

Also, if you have the space around your air handlers, you might even get away with the cheaper AprilAire 600, as it does't have it's own fan, and just uses the main air handler's fan. I believe it is the same pad, so the same effectiveness as the 700.

How effective would it be compared to a steam unit in terms of getting the humidity up ?

I've talked to 2 HVAC sales people in Calgary and both told me they are installing steam humidifiers left and right as the solution to home humidity problems around here. But I don't know if they are trying to sell me something or if its what I really need. The biggest turn off to me about the steam units is their operating cost for electricity. 10+ amps at 240VAC for 2 units is no small load ! Basically 5KW or 50 cents an hour when they are running. Could get expensive pretty quickly.

Originally Posted by BigBear23

They appear to have insufficient capacity to keep the humidity up.

FWIW, we currently live in a similarly sized house. Probably 4500 ft^3 finished on 3 levels, 10 foot ceilings on main and upstairs, 8 foot in the basement. Its also in Calgary.

It has twin force air natural gas furnaces with the same Honeywell humidifiers as the new house. The current house also has a humidity problem in that the air is too dry in the winter. However, the current house doesn't have as much hardwood and its the manufactured hardwood which doesn't seem to be nearly as sensitive to humidity. I have taken to over riding the furnace control and leaving it on "fan" most of the winter so that the humidifiers are running constantly.

It seems to me its a real problem to keep the humidity up in large homes around Calgary and I've heard this from may other people as well.

I think my first course of action is to increase the capabilities of the humidifiers.

This response is going to cross over to your other post regarding fresh air change. If two of those honeywell drum humidifier aren't keeping up, then the house is very leaky. I'd say in this case, your first step would be to have a blower-door test done on the home, and find the major leak points, and tighten up the envelope. Of course, if you get it too tight, you will then have to look into the fresh air exchange, but it will be well worth it in the end. Either way, it seems both questions being asked are pointing to the same first step.

Originally Posted by CraziFuzzy

Is there a problem with the current honeywell humidifiers already in place?

They appear to have insufficient capacity to keep the humidity up.

FWIW, we currently live in a similarly sized house. Probably 4500 ft^3 finished on 3 levels, 10 foot ceilings on main and upstairs, 8 foot in the basement. Its also in Calgary.

It has twin force air natural gas furnaces with the same Honeywell humidifiers as the new house. The current house also has a humidity problem in that the air is too dry in the winter. However, the current house doesn't have as much hardwood and its the manufactured hardwood which doesn't seem to be nearly as sensitive to humidity. I have taken to over riding the furnace control and leaving it on "fan" most of the winter so that the humidifiers are running constantly.

It seems to me its a real problem to keep the humidity up in large homes around Calgary and I've heard this from may other people as well.

I think my first course of action is to increase the capabilities of the humidifiers.

Is there a problem with the current honeywell humidifiers already in place? if it is just a control issue, I'd look at doing a thermostat/humidistat upgrade, and continue to run what you've got.

Originally Posted by BigBear23

Would the AprilAire 700 be better than the typical drum style evaporative humidifiers ?

It seems to have a similar control to the 800 model, ie outside temp sensor.

http://www.amazon.com/Aprilaire-700-...d_sim_sbs_hg_1

I wouldn't base the humidifier choice on the controller - in most cases, you'd be better off replacing the main thermostat with one that controls humidity as well, so it is all controlled as a single system. For starters, you may NOT want the humdifier running unless the heater is also running, simply because you end up getting 'cool' air blowing out the vents when this is happening (it is essentially an evaporative cooler). Really, the only good way to coordinate this is with a singular controller for both temp and humidity. Most that support this also support an outside temp sensor, to prevent dew formation on the windows. Also, if you have the space around your air handlers, you might even get away with the cheaper AprilAire 600, as it does't have it's own fan, and just uses the main air handler's fan. I believe it is the same pad, so the same effectiveness as the 700.

Would the AprilAire 700 be better than the typical drum style evaporative humidifiers ?

It seems to have a similar control to the 800 model, ie outside temp sensor.

http://www.amazon.com/Aprilaire-700-...d_sim_sbs_hg_1

Best big home humidifier setup. (steam versus evaporative, etc.)

We just bought a new (to us) house in Calgary, Alberta. Its a 2 story, built in 2007, 5,000 ft^2 finished, including the basement, 9 foot ceilings throughout. Hardwood everywhere on the main and upper floors. Finished in place floors, hard wood built ins, solid hardwood doors. Its appears to be a very well built home. Its probably pretty air tight.

Calgary is extremely dry in winter. Its dry when its cold out (-20F) and even dryer when the chinook winds roar through. Think 32F, 30 MPH winds, 10% relative humidity.

The house is deficient in humidity. The hardwood in the floors has shrunk slightly. We've been advised to do something about the humidity problem ASAP or risk long term damage to the floors.

The house has an on demand natural gas hot water heater and hot water storage tank feeding heat exchange coils in dual forced air heat exchange units, one for the main floor and one for upstairs. The basement has its own recirculation fan and ducting and in floor hot water heat coils.

The house also has dual AC.

The forced air heat exchangers are each equipped with Honeywell drum type evaporative humidifiers with simple local humidistats.

What should we install in this house to maintain the humidity at 30% or more through the worst conditions Calgary has ?

Thus far the best option seems to be dual AprilAire 800 steam humidifiers. I'm liking them over the GeneralAire steam unit because of the controller and the fact it starts up the fan to sample air humidity from time to time and its got an outside temperature sensor.

However, these units seem to draw a lot of electricity ! Is there any way to humidify this house with an evaporative humidifier or is there such thing as a natural gas steam humidifier ?