New House: Would You Insulate Foundation?

[ItsNemo]

Update: I decided the cost is too high so I am not going to do the exterior hard foam insulation. If I could be there in-person right now I would do it myself, but I am still here finishing work and selling the current house until early Aug. So doing the work myself now is just not an option. Talked to builder and even he agreed the cost from the subcontractor seemed high. It is so easy to let costs start to spiral upward, trying to keep that to a minimum.

Cincinnati is not that sever of winter climate, as pointed out further north gets a lot worse cold. I know it seems hard for many to believe, but I actually get more snow at my current house here in NM, at 7100 ft elevation, than Cincinnati does. The bigger difference is here we get more sun and typical winter day temps can get above freezing more often. I also lived in the Cincinnati area in the past, so I know what I am getting into.

Wanted to say thanks to all who replied, it helped in my decision process.

When I built my last house, the only things I regret are the things I didn't do. I wish I had spent another $20k on a few things that I can't change now. In the grand scheme it's a drop in the bucket on a house build and in my case, I wouldn't have missed the money.

 

[Jackfre]

My question is what is the flashing detail on the top of the wall. I guess you would run your sill over top of the insulation and than flash down over it. That alters the wall dimensions. Or I guess you could make a 45* offset flashing to cover it. That will be exposed to the elements so galvanized or Aluminum? How will that look?

 

[yeldogt]

My question is what is the flashing detail on the top of the wall. I guess you would run your sill over top of the insulation and than flash down over it. That alters the wall dimensions. Or I guess you could make a 45* offset flashing to cover it. That will be exposed to the elements so galvanized or Aluminum? How will that look?

Jack -- that's the problem. In europe where this is done they take the outside insulation all the way to the roof -- and they extend the insulation horizontally away from the house to warm the footing. It's all done for a different reason -- it really grew out of the shallow slab/ partial basement model.

It's the same with ICF -- it's designed to go all the way to the roof.

Problem arise when hybrids are used -- The other solution is to use 2x8 walls ... I have seen this ... crazy way to build.

What's the temp of the ground 8' down in the winter -- how is this more important than the roof ? Answer -- it's not. An uninsulated basement with 50degree earth outside has a very low heat load -- and less AC load. Most basements are uncomfortable because of moisture/ high humidity and leaks -- no one every properly seals the foundation top or insulates the rafter ends/ rim.

 

[Firebrick43]

Instead of studding out the interio and insulating between, look up the "InSoFast" system. It like half of and icf wall. Looks expensive compared to just insulation but compare it to the studs, plastic, and labor it cost effective and no worries about moisture degrading studs.

Also make sure your water proofing includes dimple board. The best waterproofing will leak due to hydraulic pressure. The dimple board ensures that hydraulic pressure can not build up.

 

[rburke65]

Flashing detail? The house isn't even built yet!

 

[buddyboy]

if you don't insulate the outside you'll need to do it inside.

one thing you need to insure, is that you have a curtain drain around the basement footers draining to daylight or to a sump pump. then when they back fill they use ROUND stone, not crushed or angular stone or clay or fill dirt.

round stone will never pack, it will allow water to flow down to your drain pipe.

if your wall is waterproofed and you have round stone against it and a drain at the bottom, then your wall will never have water pressure against it. so even if it does crack it the chances of it leaking is super low.

if you do this you should never have water sitting next to your basement walls

 

[Firebrick43]

if you don't insulate the outside you'll need to do it inside.

one thing you need to insure, is that you have a curtain drain around the basement footers draining to daylight or to a sump pump. then when they back fill they use ROUND stone, not crushed or angular stone or clay or fill dirt.

round stone will never pack, it will allow water to flow down to your drain pipe.

if your wall is waterproofed and you have round stone against it and a drain at the bottom, then your wall will never have water pressure against it. so even if it does crack it the chances of it leaking is super low.

if you do this you should never have water sitting next to your basement walls

Crushed stone works just as well as long as it's had the fines graded out. You can't pack number 8's to the point water won't run right through it. That being said River Rock is many times less expensive, depends on location. River Rock just needs scooped out of the ground and graded/screened so therefore it takes less fuel to end up as an end product.

Most of the time hauling to site cost more than the product. Here in my county we have none of the natural limestone products so common in Indiana but has a lot pea stone naturally occurring. Pea is about 12 dollars a ton delivered and crushed stone is 60 miles away but about 22 a ton delivered. They have no natural pea up there so the prices are nearly flipped due to hauling.

 

[Casey69]

I am not an authority on this, but I seriously doubt you will live long enough to save $4,000 on your heat bills by insulating the outside walls since you are already planning on insulating the inside walls.

that'd be my thought as well. i can see a benefit, but it wouldn't be worth $4K.

 

[wasfuzz]

When I lifted my house and put in a new basement my contractor convinced me to have the outside spray foamed and it acts as insulation and water seal. Glad I did it, seem to be holding up well and keeps the basement nice and warm or cool depending upon the season. Cost me $1400 to have whole house basement done. I had them spray up over the sill by 18" to take care of any drafts in that area also. House was built in 1854, but remodeled and maintained. Just how do you seal the seals when they are 12" hand hewn logs?
Just have to keep the foam exposed to UV light painted which I did, used a grey concrete color and you can not tell from the driveway its not block.

 

[yeldogt]

When I lifted my house and put in a new basement my contractor convinced me to have the outside spray foamed and it acts as insulation and water seal. Glad I did it, seem to be holding up well and keeps the basement nice and warm or cool depending upon the season. Cost me $1400 to have whole house basement done. I had them spray up over the sill by 18" to take care of any drafts in that area also. House was built in 1854, but remodeled and maintained. Just how do you seal the seals when they are 12" hand hewn logs?
Just have to keep the foam exposed to UV light painted which I did, used a grey concrete color and you can not tell from the driveway its not block.

This is done around me -- only as a retrofit. It not the preferred way building new.

I love foam inside -- no matter the construction ... foam seals it up

 

[toyotadriver]

I built a house on a basement and put 2 inch rigid foam against the concrete on the inside before the walls were studded out. Basement stays nice and comfortable....a little cooler than the main part of the house but that's to be expected. It's not musty at all either. Of course, we planned the layout very well so in the recent VERY wet spring we had, lots of people had wet basements but ours was dry. Our layout and good gutters prevented any excess water accumulation near the foundation.

 

[nelstomlinson]

I would not consider omitting the insulation. Your basement will be comfortable if you insulate it, and won't be as comfortable if you don't. Insulating the outside will make condensation on the inside less likely, and will reduce the likelihood of mold.

What is the year-round average temperature where you are building? That is roughly the temperature your ground will be at, down under the basement floor. If the year-round average temperature is room temperature, you don't have much need for insulation. If you live in a temperate zone, you do need insulation.

Money in the bank can run out. Oil in the tank can run out. Insulation can never run out. Insulate.

Put hard foam board under your footings, under your slab and around your basement walls. Ordinary 10 PSI Dow Styrofoam foam can handle 1,440 pounds per square foot, so don't let your contractor BS you out of putting it under your footer.

Here in Fairbanks, AK, the year round average temperature is about 34F. I used 4" to 10" of blueboard insulation under and around my basement, and I probably should have used more. Your two inches will probably be plenty across most of the Lower 48. Outside of the Florida Keys or Hawaii, no insulation will be a mistake.

Edited to add:
I just went back and read the other replies. There are a lot of comments from people who have no understanding of the topic. How can you tell they don't know what they are talking about? They tell you not to put foam on the outside.

 

[dw1]

What if you framed the outside basement walls and spray foamed them and the outside wall joist cavities? would this give you a better insulation rating than the foam board? Seems this would be a better investment but I am not sure of the $4K price, I know spray foam is kind of expensive, but not sure how expensive yet!!

 

[NUTTSGT]

Update: I decided the cost is too high so I am not going to do the exterior hard foam insulation. If I could be there in-person right now I would do it myself, but I am still here finishing work and selling the current house until early Aug. So doing the work myself now is just not an option. Talked to builder and even he agreed the cost from the subcontractor seemed high. It is so easy to let costs start to spiral upward, trying to keep that to a minimum.


Wanted to say thanks to all who replied, it helped in my decision process.

That answers one of my questions. You are there and the new house is here, so you are unable to do it yourself.

I had found an ad last night in one of the Free Autotrader mags advertising a factory screw up on insulation. I think they were 4'x9'x3" (maybe 4") sheets for $13ea...regular price $30. I was going to take a picture of the ad but forget as I was at work last night. Although it wasn't in Ohio, it was close enough in Indiana to make it worth the drive in my opinion.

 

[yeldogt]

I would not consider omitting the insulation. Your basement will be comfortable if you insulate it, and won't be as comfortable if you don't. Insulating the outside will make condensation on the inside less likely, and will reduce the likelihood of mold.

What is the year-round average temperature where you are building? That is roughly the temperature your ground will be at, down under the basement floor. If the year-round average temperature is room temperature, you don't have much need for insulation. If you live in a temperate zone, you do need insulation.

Money in the bank can run out. Oil in the tank can run out. Insulation can never run out. Insulate.

Put hard foam board under your footings, under your slab and around your basement walls. Ordinary 10 PSI Dow Styrofoam foam can handle 1,440 pounds per square foot, so don't let your contractor BS you out of putting it under your footer.

Here in Fairbanks, AK, the year round average temperature is about 34F. I used 4" to 10" of blueboard insulation under and around my basement, and I probably should have used more. Your two inches will probably be plenty across most of the Lower 48. Outside of the Florida Keys or Hawaii, no insulation will be a mistake.

Edited to add:
I just went back and read the other replies. There are a lot of comments from people who have no understanding of the topic. How can you tell they don't know what they are talking about? They tell you not to put foam on the outside.

The OP is in NM -- I'm in the mid-atlantic .. and have built in SC and as far north as Maine. You are in Alaska for gods sake ... slightly different.

I had a full basement in CT w/o any insulation for a couple of years and the kids played down there with out any issues. It was dry and warm. Exterior insulation will not fix a leaky foundation or a site not properly drained -- nor will it fix improper rim construction/ insulation. There build loop geo systems around me no deeper -- 55 degree earth in the winter with no air infiltration is easy to fix with not much R

Lots of basements leak -- and have no HVAC -- cold air falls.

 

[jfitz]

Up here in the Great White North our exterior walls are water sealed on the outside with a material that looks similar to driveway sealer (Not sure of the composition). Its sprayed on. The interior walls are then studded and at a minimum R14 insulation is put in with a plastic vapour barrier over the insulation and then drywalled. I think the code now is for R20-22 in the walls. Makes the basement nice and cozy. The latest craze now, and especially for garages is to put radiant heat in the cement floor. My buddy actually did his garage this way, plumbed the floor then poured a 4" slab over the pipes. Makes for a very enjoyable working environment when your back is on the floor in the winter time

 

[LB-1911]

Update: I decided the cost is too high so I am not going to do the exterior hard foam insulation. If I could be there in-person right now I would do it myself, but I am still here finishing work and selling the current house until early Aug. So doing the work myself now is just not an option. Talked to builder and even he agreed the cost from the subcontractor seemed high. It is so easy to let costs start to spiral upward, trying to keep that to a minimum.

Cincinnati is not that sever of winter climate, as pointed out further north gets a lot worse cold. I know it seems hard for many to believe, but I actually get more snow at my current house here in NM, at 7100 ft elevation, than Cincinnati does. The bigger difference is here we get more sun and typical winter day temps can get above freezing more often. I also lived in the Cincinnati area in the past, so I know what I am getting into.

Wanted to say thanks to all who replied, it helped in my decision process.

Thanks for the update.

 

[toyotadriver]

I would not consider omitting the insulation. Your basement will be comfortable if you insulate it, and won't be as comfortable if you don't. Insulating the outside will make condensation on the inside less likely, and will reduce the likelihood of mold.

What is the year-round average temperature where you are building? That is roughly the temperature your ground will be at, down under the basement floor. If the year-round average temperature is room temperature, you don't have much need for insulation. If you live in a temperate zone, you do need insulation.

Money in the bank can run out. Oil in the tank can run out. Insulation can never run out. Insulate.

Put hard foam board under your footings, under your slab and around your basement walls. Ordinary 10 PSI Dow Styrofoam foam can handle 1,440 pounds per square foot, so don't let your contractor BS you out of putting it under your footer.

Here in Fairbanks, AK, the year round average temperature is about 34F. I used 4" to 10" of blueboard insulation under and around my basement, and I probably should have used more. Your two inches will probably be plenty across most of the Lower 48. Outside of the Florida Keys or Hawaii, no insulation will be a mistake.

Edited to add:
I just went back and read the other replies. There are a lot of comments from people who have no understanding of the topic. How can you tell they don't know what they are talking about? They tell you not to put foam on the outside.

They also don't live in Fairbanks AK either. What you'll need for insulation there is WAY more than what the OP will need.

Green building site has a lot of information about insulating basements. It's a good way for most of the US to install the rigid foam on the inside instead of the outside.

I bet you don't have issues with termites where you live. Come down south and termites become a problem and termites love burrowing through foam.

 

[yeldogt]

Up here in the Great White North our exterior walls are water sealed on the outside with a material that looks similar to driveway sealer (Not sure of the composition). Its sprayed on. The interior walls are then studded and at a minimum R14 insulation is put in with a plastic vapour barrier over the insulation and then drywalled. I think the code now is for R20-22 in the walls. Makes the basement nice and cozy. The latest craze now, and especially for garages is to put radiant heat in the cement floor. My buddy actually did his garage this way, plumbed the floor then poured a 4" slab over the pipes. Makes for a very enjoyable working environment when your back is on the floor in the winter time

Are you sure on the plastic ? That's sound risky ... I never use plastic in a basement ... never . I never use plastic ... period.

Basements need to be dry so everything can dry to the inside.

 

[woodzy]

I built in the Toledo area and most good builders include 2" on the outside everywhere below the ground where there is basement walls. Did not do it on the porch areas just area of the living space. I finished my basement and on the wall I finished I also sprayed foam on the inside and then added fiberglass.

I would do it again in a heartbeat.