Slab houses

[halleesmom]

Those of you that have a house built on a slab, do you have any problems keeping the first floor warm in the winter? I live in Indiana and winters can get pretty cold. I like to keep the temp at 76.

[bunnymendelbaum]

My sister's house is also slab-on-grade and she is in Indianapolis. She has mentioned that the first floor is hard to keep warm.
It might mean that your slab or foundations were not properly insulated.

(We plan on doing a slab-on-grade house here in NC, but we will have radiant floor heating.)

[kitty]

Most of our house has a full basement but our mudroom/laundry room/half bath area is an addition on a slab and it is noticeably colder. The same tile floor that we have in our kitchen continues into the mudroom and you can instantly tell when you cross over from the basement part to the slab part.

The GC had recommended putting those electric heating mats underneath the tile but we opted against it because it isn't area that I lounge around in often and our state has some of the highest electricity rates in the country. If it had been my master bath, I definitely would have gone for it.

[tarheels]

Nope, but blessedly my winters don't speak at all to Indiana's.

I'm sort of interested to hear why you think this is a slab problem. Personally, I think a slab would be warmer than a crawlspace if you're not living somewhere where the ground freezes (ie, Russia). I think this is an airflow problem - heat simply rises. If you have ceiling fans, do you have them on low going in reverse on the first floor? It genuinely makes a big difference. (Although there's that weird northern bias against ceiling fans, so you may not want to install one, but I'm telling you it makes a big difference.)

[tarheels]

Mar 25, 2013 14:33:32 GMT -5 kitty said:

Most of our house has a full basement but our mudroom/laundry room/half bath area is an addition on a slab and it is noticeably colder. The same tile floor that we have in our kitchen continues into the mudroom and you can instantly tell when you cross over from the basement part to the slab part.

Hm, like I was saying in my post, I think this is an airflow thing, not a slab thing.  Isn't the addition simply colder because it's not sitting on top of a heated room, whose heat is all rising to its ceiling/the floor for the rest of the house?

[bunnymendelbaum]

I think it is both tarheels.

My sister has forced air heat. That air rises to the second floor quickly.

BUT, if your slab is not properly insulated (or not insulated at all) then you are getting all that cold from the ground under your house.

If a house is on a crawlspace, the structure is wood and it is insulated.

[kitty]

Mar 25, 2013 14:46:29 GMT -5 tarheels said:

Mar 25, 2013 14:33:32 GMT -5 kitty said:

Most of our house has a full basement but our mudroom/laundry room/half bath area is an addition on a slab and it is noticeably colder. The same tile floor that we have in our kitchen continues into the mudroom and you can instantly tell when you cross over from the basement part to the slab part.

Hm, like I was saying in my post, I think this is an airflow thing, not a slab thing.  Isn't the addition simply colder because it's not sitting on top of a heated room, whose heat is all rising to its ceiling/the floor for the rest of the house?

Well we don't usually turn on the heat in our basement (which is under the kitchen) but I'm sure the air in the basement is warmer than the ground outside.

[emoflamingo]

I haven't had an issue at our old house (which was slab) but we only had one level. I would check your fans and see if that helps.

[kaylie]

My MIL's house has a partial basement and the rest is on a slab. The rooms that are on the slab are noticeably colder in the winter.

[stephm0188]

No. I feel like it's warmer, actually. The furnace is in the center of the house and all the duct work for the first floor is in the slab. It keeps the floors pretty toasty, even the tile.

[halleesmom]

Mar 25, 2013 14:39:36 GMT -5 tarheels said:

Nope, but blessedly my winters don't speak at all to Indiana's.

I'm sort of interested to hear why you think this is a slab problem. Personally, I think a slab would be warmer than a crawlspace if you're not living somewhere where the ground freezes (ie, Russia). I think this is an airflow problem - heat simply rises. If you have ceiling fans, do you have them on low going in reverse on the first floor? It genuinely makes a big difference. (Although there's that weird northern bias against ceiling fans, so you may not want to install one, but I'm telling you it makes a big difference.)

To clarify, we are currently building a house. My dad owns a HVAC company and mentioned we may have problems keeping out first floor warm with a slab house and the vents in ceiling of the first floor.

[boiler717]

We have a basement but we have one set of friends who have a slab and their house is freezing. I wear two pairs of socks over there and my toes still get cold standing on their floors. We are in Indy.

[FoxInFiji]

Yes slab foundations transfer a lot more heat out of the house than a crawlspace or better yet a basement! This is because the farther down underground you get the less heat transfer you have. The soil acts as an insulator essentially.

ASHRAE graphic:


Most of the heat loss in a basement wall is from the top couple feet with very little of it being lost at the bottom. With a slab foundation the biggest loss is at the sides of the slab not the center of the slab. The insulation is more crutial on the sides of the slab and around the footings than it is under the slab. There is a special F-factor used to calculate the loss through the sides of the slab.

So even if the crawlspace or basement isn't heated it will still be warmer than a slab on grade foundation. It is very uncommon for a home in our cold WI climate to have a slab foundation because of this. I'm surprised they do them in Indy actually. But I guess it's just costs. It's a lot less to pour a slab than dig a basement.

Here I wrote a post on calculating your home's heating and cooling loads if you want more info.

And LOL TH&R you don't have to be in Russia for the ground to freeze! Here's the frost penetration depths across the country:

[halleesmom]

Thanks Fox, that's great info. I wonder how this builder can say their homes are energy efficient if this is such a huge problem.