Does a concrete slab on grade need to have radiant heating in the floor? Will it be warm enough to insulate under it with foam. I live in a cold northern climate and would like to heat with a masonry heater and not go to the expense of putting in radiant in-floor. Does anyone have experience with living with a concrete slab on grade?
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What's going to be the finish over the concrete?
Carpet----- you'll be fine with no radiant.
Tile------ You're going to notice a temperature difference between the floor & the rest of the room if you're walking around barefooted.
In search of a new tagline, don't worry I'm sure I'll find one that will bother somebody.
;-þDoes it have to have radiant heat? Only if you want it to be warm to your stocking feet.
Will it be enough to insulate it with foam? That depends on the insulation value and tightness of the building envelope, how much foam is installed sub-slab, whether you've used slab-edge insulation (where most heat loss from a slab occurs), and on whether you plan to cover the slab with a less conductive material such as wood or carpet.
If you build the masonry heater right on top of the slab, it will transfer some heat to the slab area around the heater.
A bare concrete floor is both a cold surface and a hard surface to stand on. I would recommend covering it with wood - I've used prefinished 3/8" T&G oak put down with mastic. Just make sure that there's a good vapor barrier under the slab (and that the slab is dry before covering) and 4" of rigid foam board. And don't forget the slab edge insulation.
Solar & Super-Insulated Healthy Homes
As plumbill points out, you will feel it. In fact, with tile it will be sort of reverse radiant-cool feeling rather than warm.
I have radiant HW in the floor and a masonry heater. In the fall and early spring when the floor is not on there is a definite cool to the sock covered feet. Of course, above the floor it is comfortable with the masonry heater going.
Once the concrete is down you won't be adding HW radiant any time soon. Give it some serious thought.
A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
I live on slab on grade, no tile, no carpet, just stained concrete. I am about 40 minutes from the gulf of mexico. My floors are cold, real cold. Have to wear socks. even with heat on floors are cold.
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two ways to screw up concrete 1) concrete driver 2) concrete finisher
Edited 1/28/2008 8:54 pm by brownbagg
Brownbagg
ever do any insualted slabs down your way? Cool floors might be an advantage in the summer though. No?
The heat isn't on in the summer.I wonder why insulate the entire slab? Wouldn't you want the heat capacity of the dirt in the middle of the slab? I can see the perimeter for obvious reasons, but not the center of a basement slab.
To tell you the truth I've never messed with an insul slab nor have I paid much attention to them since they seem like they do not carry an advantage to to those of us in cooling envrionemnts. I was just asking BB if he had done any down his way out of curiosity and if so maybe I've been missing something that I should indeed been paying closer attention to.
Oh sorry John, I was responding to two different posts. Just the no heat in the summer part was directed at you.
>Wouldn't you want the heat capacity of the dirt in the middle of the slab?
I've seen references to this as an option in various discussions. Would be interesting to see some thermal models or experimental results to see whether the ground actually heats up & stabilizes, or just keeps draining heat away. If the water table is fairly high, you're guaranteed to lose a lot of heat. Dry soil would probably act as a nice thermal mass to stabilize the house temp.
Taking the concept further, you get into the PAHS (Passive Annual Heat Storage) concept, which a couple people discuss on this forum frequently. Maybe they'll pipe up.
Don
I agree with Riversong - don't forget the edge insulation. My slab on grade had no insulation. Funny how the snow melted on the outside fo the house at -20 till I covered it over.
Slab on grade was not my first choice for a house. I prefer to have good access for mechanical and electrical for those required alterations. But it was those sweet words from my wife - "honey the house is perfect you don't have to do a thing". I pulled the carpets from three bedrooms on the first night I moved in.
If I had the choice I would go with hot water infloor without hessitation. I didn't want to redo the entire house so I left the new oil boiler with HW baseboards.
I went with engineered hardwood flooring on top of DELTA FL (dimpled plastic). It seems to have worked out fine. I had carpeting before but wasn't too crazy about it being slightly damp during summer time condensation.
I had ceramic tile in the kitchen. It worked for me but wasn't my favourite. My wife always wanted ceramic instead of linoloeum. Thought it was great until she could no longer stand after working most of the day doing some baking. Ceramic floor was cold all the time. Pulled all the carpet and ceramic on the slab floor. Radiant in-floor would have made a big difference.
It would be so easy to put a little tubing and good insulation in there even if you put it in at a half lineal foot to square foot ratio and don't hook up the boiler until you win the lottery. It's just so much easier to put it in there in the beginning and like Riversong says goe nuts on the foam, it's just such a pain to wish you had done it later. (I have a really good friend with a solar house with no tubing in his slab that has been kicking himself for years about it)
M
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"You cannot work hard enough to make up for a sloppy estimate."
I'm kicking myself for not putting it in the detached shop/garage.A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
What would you do about an exposed edge of the slab to minimize heat loss?
I'm thinking of a similar application but I'm concerned that in a MN climate it would waste a tremendous amount of energy. Perhaps just good landscaping around the structure to get the soil right up to the bottom of the block? Foam underground. (assuming slab on grade with one block course) Any ideas?
Sorry, my experience with slab on grade is zip.
A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
If you just wanted to warm some specific areas, like bathrooms and kitchen floors, you might want to consider an electric radient mat. These systems have programable thermostats that can keep the floors at specific temps at different times of the day.
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
As a builder in Michigan I place 1" foam board under the entire walkout basement floor and 1" down the frost wall to insulate the basement floor (without radiant heat). This will minimize thermal transfer and provide a more comfortable floor. It may still be cool but much better than without the foam. I would suggest running pex thru the slab and 2" of foam under the slab so that if you want to add radiant heat, the option to do so will be easy. The cost to add pex and the additional foam will cost less than $1000. for a 1500 sq. ft. floor. The combi core hot water heater will add $500. to your initial cost if installed when you build.
Good Luck
Thanks for all the feedback. I should have been a little more specific. I am looking at building the house with ICFs so this would take care of the slab edge insulation. The bedrock on my property is fairly close to the surface 3 feet or less and I am looking at some solutions so that my house is not jacked up into the air to get a basement. I do not want steps to get into the house.
The slab edge question was not about your application. It sounds like you have a little knowledge. Just enough to be dangerous. You have the same options for heat with a slab as with a full basement. You can run forced air around the perimeter under slab in PVC ducts or install an insulated system in the attic, i.e. a high velocity system. You can run radiant, radiators, or any combination. There are no limitations on the system (actually more options) with a slab on grade, just a couple different materials. It sounds like you have some ideas and need to take the next step of finding a designer or design/build contractor. This is a simple problem in the scope of your house. But I think the paragraph above should answer your questions.
I live in a slab on grade home in a northern climate such as being discussed. The way I understand it, you must have in-floor heat in this type of climate for a slab on grade house to keep the frost away from the foundation. Without that heat, frost will get under the slab and heave it. It's the only way that system will work in this climate.
Along with the in floor heat and foam under the slab you should put 2" foam 4' out and around the entire perimieter of the building to help keep the heat under the building. I can go outside right now and dig to china right next to my house, but 5' away is froze solid.
Again, without it, you will have very cold feet as well.
upnorthframer
"If you think education is expensive, try ignorance!!!"
The heat of the building is keeping your foundation from freezing. They have been building slab on grade for a long time before you could buy radiant heat systems. Typically large PVC pipes are put in the ground around the perimeter just inside the exterior frost foundation. They are sealed and connected to a downdraft air handler somewhere. The only foundation insulation is inside and outside the frost foundation. I can't see a reason for more insulation for a radiant slab either. The additional heat mass of the dirt below the center of the slab would be beneficial to the heating efficiency of the system IMO.see what I'm saying?
The dirt mass your refering to is considered a heat sink. If you did this it would be extremely difficult to regulate the heat in your house, ecspecially in the spring and fall when it's 60 degrees during the day and 25 at night. That is why a majority of people building on a slab place 2" foam under the entire slab and out 4' around the perimiter.
I understand your pipe method, however, wouldn't it be easier, more comfortable, and probobly the same cost to do in floor heat? Hydronic heat is relativly inexpensive in my opinion.
Maybe I should ask WHY the origional poster doesn't want hydronic heat????
upnorthframer
"If you think education is expensive, try ignorance!!!"
That makes sense. The air and light frame will heat up much faster in the sunlight. Good point. I wonder if increased circulation throughout the home would help this and allow you to use a larger heat sink more effectively? I would spend the little extra for a radiant system, but you still need to cool the house. That means a forced air system. In which case he's either going in plastic underground or high velocity in the attic. I think the best scenario would be a high velocity hydronic system with in floor heat. But the reality of a budget may dictate a forced air system only if he needs to heat and cool with one system. In that case I would go with the in floor perimeter forced air system. It will keep the floors warmer. Not nearly as well as a radiant system, but certainly better than an attic system.
I mainly see split unit air conditioners for slab on grade houses. Mainly because of cost and ease of installation. In northern climates, you really only need AC a handful of days, so they are sufficient. Ecspecially considering they take a lot of the humidity out of the air. Just my 2 cents.
upnorthframer
"If you think education is expensive, try ignorance!!!"
I suppose that is an option. Still two systems to buy. And I personally think they're kinda ugly.
I'm in Minneapolis and my AC runs quite a lot in the summer. I remember having window units in college. The comfort level between a window unit (essentially the same as a split unit for this purpose) and a central system is night and day. But it would depend on the design of the home and exactly where he is and... If he's living in a one room shack, A split system is probably the answer, or maybe just bigger windows. ;)
My house is two 1/2 stories with frost walls and slab. It is on a hillside. The street entrance is at the top level and you go down.When I built in 79 radiant was not common and not even heard about in this area Kansas City.I had to fight and fight to find an HVAC dealer to properly heat the bottom level. Although it is the main living area (LR, DR, kitchen) and heavyly windowed on 2 sides all of the contracts kept saying "and we will stick a couple of registers in the ceiling for the 'basement"". I knew that would be cold in the winter.I ended up with 2 completely separate systems. The problem is that both furacnces are way, way, way oversized.On purpose I only installed AC on the upstairs system. It is not perfect, but it also keeps the downstairs reasonably cool.If I was building again I would look at using radiant in the lower level and hydro air/AC for the 2nd floor, with a couple of registers in the lower level ceiling to get just a bit more AC down there. Or maybe cheap radant, with a WH for the 1st and ductless mini-split heat pump for the 2nd floor..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
My house was built like that in 79.Since then studies have shown that there is still significant heat loses in the uninsulated part of the floors.The problem with trying to use a the ground as a heat mass is that it takes way too long to get it hot and then it is giving heat by during the time that the AC is running.However there is a way of using the earth mass. VATom has that in his house. But the heat that is being stored is from the enviroment and not the house..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Kaslo,
I just installed in-floor tubes in the walkout basement of my new house. It was cheap and it was easy. I insulated 1400 sf of basement slab for about $900, including the manifold. The insulation was another 600 or so. For $1,500 I have it ready to go. I will hook it all up when I have the extra dough, but with a water heater it may not be much $ at all to do.
You will kick yourself later if you do not install it now, even if you do not hook it up now.
I did learn that the ground should be well prepped (evened out) before insulating, to avoid a "wavy" floor (could make some spots of the concrete pour a bit thin). A bit of a pain to remedy once the insulation is down--use a string or similar to check for high and low spots. Good luck--you'll never regret doing it, but may regret not doing it!