1ST FLOOR Radiant floor heat heating the basement

N

We just built a new home, 1st floor is 5300 square ft with propane radiant floor heat, our basement is unfinished with prefab insulated wall system with no windows only one egress 4ft wide. Our basement is so tight that we had to add a dehumidifier because our wood floors were cupping. Temperature in basement is 75 degrees - 1st floor is 68 degrees, Humidity in basement is now 40 to 45 degrees and 1st floor is 35 degrees.

QUESTION:



The basement is warmer than the 1st floor. Are we suppose to have some kind of insulation between the 1st floor and the basement ceiling to push the heat up.



Thank you

nancy

bruce_21

yes you need insulation

to slow down the heat flow and direct it upward. The insulating R-value of the wood floor is something like 1 to 2.5 depending on the species and thickness. You should have an insulation R-value of at least 6 times what your floor is to ensure that the heat mostly goes up. We like to have a foil reflective face right below the pipes especially if they are "stapled up" to the subfloor.

Gordy

Type of RFH

What type of radiant floor heat was installed? Staple up, Suspended tube, Sandwich, warmboard, gypcrete?  Was there tubing installed in the basement slab? What type of floor coverings are on the main floor I see there is wood flooring in the basement.



 I agree with Bruce you need to insulate the floor. The installer should know this to advise you on doing so if it was not in his quote to provide a sub to insulate. Being the house is new maybe you are still finishing things up?



 New homes will out gas a lot of moisture from new building materials takes a season to stablize. I hope the wood floor installers let the flooring aclimate to the enviroment before installing your flooring.





Gordy

Brad White

Thermal Anvil

Insulation, no question.



I do have a question, Nancy, regarding your temperatures and humidity numbers. You say, "Humidity in basement is now 40 to 45 degrees and 1st floor is 35 degrees". By this I presume you mean RH or relative humidity.



Based on these numbers, you have quite a bit of specific (="actual") humidity in your basement. Normally the warmer a space the lower the RH, all things being equal and your situation is reversed, by your numbers. To have your basement at 75 F. and 40-45% RH you have between 52 and 58 grains per lb. of air.



(OK, I understand... Just take my word for it!)



Your upstairs at 68F and 35% RH has a relatively modest 35.6 grains per lb.

What this means is that your basement has between 46% and 62% more actual moisture than the upstairs, a significant difference.



The concern I have is, until you reduce that humidity (as you seem to be in the process of doing), I would not yet try to reduce the temperature.

(Now, your humidifiers, if the Santa Fe type, DO add heat so that may be part of your source and a benefit to the process. That is fine. But if the radiant heat is driving that temperature up, read on.)



If you do not reduce the actual humidity but reduce the temperature say ten degrees, to 65F. your relative humidity will rise to the high 50% range (56-57%). If to 60 degrees,  it would be nearly 70% which is not healthy in the long term.



Not to alarm you, just get the RH down, check the moisture content of the wood structure and once that is down to the recommended levels (usually 8-12% but ask), before insulating the underside of the structure.

tim smith

Re: basement heat

I would suggest maybe an HRV ventilator for the basement with maybe a dessicant dryer in line if needed?? What you think Brad. Then insulate the underside of floor. Make sure they are controlling the water temps to floor properly so you are not exceeding 82 degree surface temps at any time. I think you will find this to correct your problems mostly. I agree that the floors needed to be acclimated until the moisture content was in line w/ floor mfrs recommendations before installing. Good luck, Tim

Brad White

What I think...

Tim- I think long-term you are right., a desiccant dryer in series on an HRV makes sense. But the amount of moisture in play right now (assuming Nancy's readings are good as I assume they are), seem too high for an HRV. The use of a positive removal unit such as a Santa Fe make sense to me now.



But you are right, long-term there is something that needs attention, for ventilation if nothing else. The desiccant is a good touch, but I suspect once the gross moisture is removed, cold outside air through an HRV should be sufficient. I am presuming a tight foundation, vapor barrier and no leaks. The fact that the basement is warm is a plus here!

4Johnpipe

Warm Basement

A few things come to mind. Yes you absolutely need insulation between floors other wise you will have a radiant ceiling. Another issue with Superior Walls which is a company used around my neck of the woods. They are installed on a tamped bed of crushed stone and can have an active de-watering piping system within the stone bedding. If that is the case the humidity can be drawing off the wet french drain system as is common practice here. Finally are you sure the "T" stats are working the correct zones???

N

1st FlOOR Radiant floor heat heating the basement

Thanks to everyone for helping us with our problem. More Information. The installer said he did not insulate when he installed the radiant floor system which is why we are not getting the true results from radiant floor heat.

He used Watts Pex orange tubing with gypsum on top. We have wood floors and stone tile in kitchen and baths. In the unfinished basement in certain areas you can see a couple of long runs of exposed pex tubing before it goes up to the 1st floor, the rest of pex goes right up to 1st floor.

The wood floors are not cupping anymore since we had to install a dehumidifier in the basement. The humidity reads 45% in the basement. About 37% on 1st floor.

I hope this helps. Thank you

N

Measurement

We are using a Springfield comfort monitor for our readings

N

reply

Thanks for your help, the installer said he did not insulate which is why we are not getting the correct radiant heat on the 1st floor

Other comments are saying not to insulate until we get the humidity out of the basement

Gordy

Lots of moisture

 From the gypcrete, poured floor in the basement, fresh building materials. As stated above I would let everything dry out before insulating under the first floor radiant. But insulating after is a must to keep up stairs zone from over heating down stairs, and vice versa.

N

Superior Wall System

Thanks for your help. The wall system was installed on soil then the stone was poured inside the walls then concrete for the basement slab. Our basement is dry. I hope this helps.

N

moisture

I forgot to mention we have been living in our home now for 2 years, is that enough time for everything to dry out?

Thank you

Brad White

Two years?

Yes, I would hope so. I would expect the moisture content to be fully stable/acclimated after six months, a change of seasons, absent Hurricane Katrina. 

Gordy

Hmmm

 I was under the impression this was recent construction. I would definitely take Brad's, and others advice as to an integral system to controlling the humidity levels in your home.



 Radiant heat is not like forced air in the aspect that forced air systems tend to dry out the home in the winter, and humidification is needed. Many sources of moisture in the home with laundry, bathing, cooking, cleaning ect.



 It usually takes my house about a month to get humidity down to the 30% range going in to the heating season, but then all is good the rest of the season with out mechanical removal. My house is 60 years old, and probably a little loser construction than yours.



Gordy