Basement floor insulation quesiton

[GSRinmyCRX]

building a house with a superior wall foundation and I am going to be pouring the basement floor soon. portions of the basement will be converted to living space down the road as space requirements extend beyond the first floor. there is a walkout at the one end about 20 ft.

I have decided not to add radiant floor heating into the slab as most people I have talked to do no use it and the I am looking to save money anywhere I can.

my question is would be the worth the money to add rigid insulation under the slab. for 2-inch would be about 2k and 1-inch would be about 1k.

my thought at this point is to go with the 1-inch to provide a thermal break between the slab and the stone/ ground.

anyone have any thoughts on this?

Thanks.
Levi

 

[Milton Shaw]

What is your location: not in your profile

 

[GSRinmyCRX]

sorry. western New York.

Levi

 

[aptdweller]

Where are you? If you are In the northern States, I think it would be worth your money. You have to think both about the cost of heating and whether you are going to get complaints about having a cold floor.

 

[sands35]

Look for used insulation supplies. Craigs list sometimes has listings. Basically $0.50 on the dollar for used stuff.

 

[Leaflessshadetree]

It depends on the dept of the basement. If it is below the frost line without insulation you have free heat in the winter and cooling in the summer.

 

[GSRinmyCRX]

it is well below the frost line except where the walk out section is.

Levi

 

[K'ledgeBldr]

I concur. I'd only be concerned about the part of the slab that would most susceptible to the "frost-line".

 

[wssix99]

You have two issues to consider: energy efficiency and comfort.

The ground beneath the slab will always be something around 55 degrees-ish. That will be great for you in the summer, but in the winter it will be a tremendous heat sink. Insulation will slow the transfer of the heat to the ground. The insulation is expensive - but you can easily calculate the energy loss and figure out the energy efficiency payback. If you are going to life in the house more than 10 years and will heat the basement like a living space, I'd expect the insulation to easily pay for itself.

On comfort, the insulation may help your heating system keep up with the demand for the space better by slowing down the heat loss. This may make the space a tad bit more comfortable, but the floor will always be cold - 55 degrees-ish. The only way to make the space really comfortable is with radiant.


I took the advice of my HVAC contractor and others on this site and put in the radiant tubes "just in case" I changed my mind and wanted to hook up the radiant in the future. (The cost of the tubes is minimal compared to the insulation.) In the first winter, I broke down, hooked them up, and the space is great.

Instead of having a system with tubes and a full boiler, you could also do an electrical mat if you just need smaller local areas to be comfortable and you can use that type of system more on-demand. They are also inexpensive to install but will cost more to run, especially if you use them for long times or over wide areas.

 

[BleedingBlue]

Not to hijack the thread, but I also have a basement insulation question.

We bought our home last year an it has a basement finished by the previous owner. I recently noticed the walls are not insulated behind the drywall. Is this normal/ok? It gets to as low as 59 in the winter down there

 

[K'ledgeBldr]

Not to hijack the thread, but I also have a basement insulation question.

We bought our home last year an it has a basement finished by the previous owner. I recently noticed the walls are not insulated behind the drywall. Is this normal/ok? It gets to as low as 59 in the winter down there

Normal? Yes; it was. Due to the fact that the majority of a basement is subterranean, the temperature and humidity tended to stay somewhat consistent. However, over the last 10-15yrs it's becoming quite apparent that major climate change is happening- so, in turn the way we finish/insulate a basement has also.

The accepted process today is XPS board attached to the foundation walls- all seams are tape sealed. Framing, then finish materials. And, depending on what region you're in adding f/glass batts between studs.

 

[BleedingBlue]

Normal? Yes; it was. Due to the fact that the majority of a basement is subterranean, the temperature and humidity tended to stay somewhat consistent. However, over the last 10-15yrs it's becoming quite apparent that major climate change is happening- so, in turn the way we finish/insulate a basement has also.



The accepted process today is XPS board attached to the foundation walls- all seams are tape sealed. Framing, then finish materials. And, depending on what region you're in adding f/glass batts between studs.

Ok, I am in Indiana. So it doesn't sound like they did anything wrong, they were just cheap.

 

[Chris705]

There is a Craig's List seller in Buffalo who has used rigid insulation for sale....look into that; folks in Rochester have bought from him with good luck...

Do not use Polyisosanurate (sp) underslab....white beadboard, pink or blue is ok.

 

[Bojans]

I decided not to insulate my basement floor but when finishing the basement I put down Dricore. It provides a thermal break and gives you the comfort of a wood subfloor on the feet. Works out to ~ $1.25/sq ft and you only need to do the areas you are converting to living space. It gives you the added benefit of allowing the floor to breath under the finished flooring.

 

[GSRinmyCRX]

I decided not to insulate my basement floor but when finishing the basement I put down Dricore. It provides a thermal break and gives you the comfort of a wood subfloor on the feet. Works out to ~ $1.25/sq ft and you only need to do the areas you are converting to living space. It gives you the added benefit of allowing the floor to breath under the finished flooring.

did some research on this in the past and thought it was over priced but when you think about all that it does for you it really is not bad price at all. I really like the idea of the wood floor feel under your feet.

I might add some insulation on the walkout end just to give the area in the frost zone some extra protection.

Thanks Guys.

Levi

 

[zak77]

If it were me building the house i'd insulate under the slab, especially considering you're planning on using it as living area and the house will be a walk-out basement. I was talking to a builder this week regarding the condos he's building which are built on slab's, abnormal for Mass but saves costs. I asked if anyone complained about a cold floor and he stated that everyone was happy since they insulate under the slab w/2" rigid foam and run the rigid foam between the vertical foundation wall and slab so as to isolate the slab from the exposed foundation. I'd suggest you do the same thing that way the slab will have thermal breaks all the way around it.

 

[GSRinmyCRX]

yes I plan to run down the vertical frost wall and probably 20 ft in from the walk out. rigid is expensive is really the draw back to doing it through the whole basement. I am not concerned with having to spend a little more down the road to make it more comfortable. I just don't see the cost benefit for 2k worth of rigid.

Levi

 

[pstnbly]

If you look into the energy standards for your state you may find that sub slab insulation is required to meet new home efficiency standards.

 

[GSRinmyCRX]

new energy code kicks in for new York I think in November this year. since we have our building permit already we are grandfathered in under the old code. the new codes would probably require it, from what I have heard a lot has changed.

Levi