Last Friday we had our heat pump / radiant flooring system turned to start heating our ICF home.  The initial excitement has worn off now that we are 4 days later and not getting much heat in the upper floors.  It's a 2000 sqft 3-story with basement radiant in 4" concrete and upper radiant in 1.5" Maxxon Therma-Floor.

A proper heat load was done and the flooring loops designed appropriately.  The heat pump is a Nordic 4 ton unit with a Giant 60 gallon buffer tank feeding the floor loops.

Basically, the heat pump is running 100% of the time and not able to get the buffer tank any higher than 85 degrees.  The upper floors are cold...  not ice cold, but cold.  The basement slab is luke warm.

As for air temps, it's warm in the basement and colder as you go up in the house.  Upstairs air temp is less than 50.  We have a few windows open due to massive condensation and moisture.

I'm assuming this is not normal.  Even with open windows, should I not be feeling warmth on the floor, even if the heated air is escaping out windows?

Outside temperature is below freezing, -5 celcius.

If you have open windows you won't keep up no matter what you’re heating with. The floor will be giving up all its heat to the air, which in turn is escaping out the windows. Is the space just not closed in yet, still in construction?

It's all sealed up, ICF to the roofline, 5" closed cell spray foam along the underside of roof.

I'm trying to combat a moisture problem that has already caused damage to the pine window frames (black mold).

Should I just close up all the windows and try to get the heat as high as possible?

I'm still confused why the floor does not feel warm at all.  I understand that with the windows open the heat will rise off the floor and escape to the outside, but should the floors not at least be feeling warm?

I'm not sure I can help answer your question, but can provide the stats on the house we're building in Calgary. The home is early stages with just the foundation wall poured now.  It will be 2226 sq. ft. two-story with a basement.  In-floor heat on all three levels using Warmboard on the main and upper, and in-concrete for the basement. 

The estimated heat load is 51k BTU/hr (for all three levels) but I expect that will be on the high side once the better windows and low air-changes are fully taken into consideration. Our local geo-exchange contractor has spec'd a Nordic 4-ton (vertical closed-loop) liquid to water unit to provide the heat.

Is your Nordic GSHP the W series or the EM series?  What is the heat load in kBtu/hr for your home?  What type of geo loops do you have?  Since our homes sound fairly similar, you probably don't need to worry about the current output, particularly since you've got windows open to dry the place out.  Unless my home is also incorrectly sized for geo-exchange, then we both should worry.

Also, are you running your HRV full out?  That should help with the moisture.

Cheers,
Guy

You should see if you can rent a couple of de-humidifiers to run in the house to speed up drying. It takes a long time in a conventional home and with your tightness, it's not migrating out. Insurance repair companies may be your best bet to rent but there are cheap ones on the market, if rental is not available.

I agree with arkieoscar, condensation and moisture is removed from the air with a dehumidifier in the winter, not by opening the windows when it's -5 degree outside.  Geothermal is a gradual heating method, where it warms the house slowly, instead of blast of hot air from a gas furnace when it switches on.  In my house, the air coming out of the vents is luke warm, any air that is warmer or hot means your AUX heat is on.  If you want to run your system with the windows open, I recommend you recalculate your heat/loss figures to include heating the outside as well. 
 
I think you will find that the system is working as it should, when you fix those leaks.  A larger problem would be where is all this moisture is coming from.  A dehumidifer uses roughly the same amount of electricity as a simular sized air conditioner unit, having a couple of them running 24/7 is going to really eat into your energy savings. Is this moisture coming from your basement?  Are the walls damp in the basement?

Ahhhh, ok, the floor won't likely feel warm since it is such a large area, basically acting as a huge radiator. Can you get an actually temp on the floor itself? I would guess since the buffer tank is at 85F the floor is around 70F which wouldn't feel "warm".

Can you check you incoming and outgoing temps on the geothermal unit itself? Running 24x7 would drop a horizontal field quite a bit, which would reduce your overall BTU output as well.

Ours ran for almost two weeks straight to get our house up to temp (which included a 16k gallon pool). Once we were up to temp we have been fine since, but that was the only time I saw the loop field below 32F and that was in the spring without outside temps in the 40F range.

And I would third what they said, borrow / buy / rent some sort of dehumidification. It will be far less expensive to run a dehumidifier than to run the heat up to push the humidity out the window.

If you have an HRV try running that on full, that will pull in a lot of dry air, but pre-warm it from the humid exhaust air. I couldn't believe how much water was running out of our when we built, it was literally a stream out the condensate drain, close to a gallon in 5 minutes, then again the house was darn near 100% humidity.

Re: techgrommit- A new building has tons (literally) of moisture in it from concrete, wet wood, the poured therma floor, still damp drywall and everything else that was in the open for months. It's really al problem with large amounts of concrete as it seems to just keep coming out.

I agree all bets are off with windows open in cold weather. Your ICF house probably has such a low design heat load that opening a few windows completely overwhelms its heat output.

I disagree with the advice to rent dehumidifiers. With outdoor temps below freezing you have an excellent source of dry air - from outdoors. It's dewpoint is by definition below freezing, drier than what a rental dehu can ever hope to produce.

Solve your temporary construction-related humidity problem by continuing to infiltrate and exfiltrate outside air through windows opened just a bit. Run heaters, simple electric resistance or possibly an oil-fired torpedo in the house to heat the air, lowering its relative humidity, causing it to pull moisture from your construction materials.

BTW do NOT rent or use an unvented propane or natural gas fired heater to do this. Unvented Combustion of NG or propane produces quite a bit of water vapor, adding to humidity and frustrating your drying effort.


If you do use any variety of fired heater beware Carbon Monoxide - we'd like you to be around for further posts.
This is all related to psychrometrics, understanding and controlling the sensible and latent properties of air mixed with water vapor.

While I agree that outside air is going to be the best for dehumidification. I just figure if you have a 1000w resistant heater running, why not have a 1000w dehumidifier running instead. You get the same amount of heat out and some dehumidification to boot. Then when it warms up start to crack open the windows for the added dehumidification, since you need the heat anyway you get both with a dehumidifier.

Not sure about the "outside dry air" theory.  Here are the current weather conditions.

• Temperature: -6
• Feels Like: -14
• Wind: E 26km/h
<!-- Wind Gusts -->
• Wind gusts: 35km/h
<!-- Sunrise/Sunset -->
• Relative Humidity: 79%
<!-- Pressure -->
• Pressure: 101.44 kPa
<!-- Visibility -->

Indoor relative humidity is around 75%, so if I bring in outside air I'm actually adding humidity am I not?

If I'm not mistaken, as soon as the relative humidity in outside air is brought into the house the relative humidity drops if the air inside the house is warmer than the outside air (since warmer air can hold more moisture than colder air).

There is an indoor humidity meter here that illustrates this:
http://www.weather.com/activities/homeandgarden/home/
Go about halfway down the page on the left side of the page and either enter your zip code (if in the US), or city, country (works for a random city in Canada I just tried). This brings up a second page where you can enter your figures.  There are some assumptions used with this calculator that you can read about. Hope this helps.

No, the outside air value of 79% is for -6oC air which is roughly 15 grains of water per pound of air.

If you indoor temp is 10oC at 75% humidity that amounts to roughly 40 grains of water per pound of air.

Most other posts are right close the windows and run the HRV on max. This way you don't loose all the energy you put into the air. Or turn off the heat pump as its fighting a loosing battle.

While I don't disagree that dehus would work, they are expensive to rent or buy.

I fought this while trying to expedite drywall in my new house. It was springtime in FL and dewpoint left me no choice but to run rental dehus.

As has been shown above, the outside air at -6 F has a high relative humidity but a fairly low absolute humidity. Simply heating fresh outside air may be more cost effective than dehumidifying indoor air.

If you have access to portable dehus (think friends and neighbors not using them this time of year) then by all means get 'em and use them. Brock is right the power they use will be added as sensible heat just like a space heater would.

I think OP meant -6˚ C for temperature, in tune with km/h and kpa - all measured on metric system.

Regards,

Masoud

Good point, M., I didn't catch that.

-6C corresponds to 21F.

At that dry bulb temperature air would still contain far less water than the air coming out of any conventional dehu, so I continue to stand by my earlier comments as to psychrometry.

Moisture still has to leave the building, one way or another. In 2006 I was asked to look at a large (McMansion) that was closed up in Oct., causing a fairly serious mold bloom. The owner/builder and the GC were able to get together and rent de-humidifiers to dry out the structure and stop the mold before it did permanent damage. It was bad enough to keep a man on duty just to empty the condensate buckets, full time for a week. They ran heat but without something to physically remove the water, it would have taken months to (in the winter) to dry it enough to stop the mold. BTW, oil fired torpedo heaters will add to the moisture just as well as unvented propane or any other unvented combustion heater.

Thanks for the great responses on this. We've been able to get the temperature up to 25 celcius, with humidity in the 60-70% range. We're wiping down the windows daily, running 3 dehumidifiers, construction fans, opening and closing doors for manual air exchange.

Our HRV should be in place by next week, unfortunately for now we don't have any systemic ventilation happening.

My main concern are the windows, they've really taken a beating. The pine frames are constantly wet, some have mold stains. I fear we're going to end up with permanently damaged windows even before we move into the place.

We're at a loss on this one, it's very frustrating to the point of losing sleep over it.

They actually paid someone to empty the buckets?  In my old house I had a hose attached to the bucket and had a Air conditioner condensation pump connected to the other end, that would pump the water out of the basement, that worked very well. 

On my new house I placed the dehumidifier directly in a sink and tape over the sensor that detects the bucket.  The sink drains directly into the basement drain thingy. Basically a hole in the floor, formed from chimmey cremic with gravel at the bottom.  It works, but I get concerned that some of the moisture its pulling from the air is coming from the drain. 

Hire someone to empty the buckets, I never heard of something so crazy. If there wasn't anyone living there, they could have placed the dehumidifiers in the sinks and tubs, taped over the bucket sensors and walked away.