How to Heat?

[Silverfox]

As stated in another thread, I just bought a tiny 440 sq ft house. I bought it to live cheap in retirement. Trouble is...it has a concrete block foundation with a concrete slab for the floor. You can see the slab sitting on top of the block foundation outside the house below where the siding stops. The house was built around 1970 and now has an old and inefficient electric baseboard heating system that is either on or off. This equals high heat bills in the Wisconsin winters. I need help in deciding the best way to efficiently heat this little place and, hopefully, keep the floor reasonably warm. My first plan is to start a few inches above the slab outside the house and install at least 3 inches of styro flat against the foundation walls all the way down as close as I can get to the frost line. Then I have to decide how to heat the place and try to keep that concrete floor warm. I HATE cold floors. I have atherosclerosis so I am cold when most people are warm. My first thought is to install those new electric base board heaters that have liquid in them and store heat. Our electric co-op has a plan that cuts the electric heat cost by 45% if you install a separate meter. Another thought I had was to incorporate a duct into that styro foundation insulation. I have a design in mind that would incoporate the duct into a super insulated channel around the perimeter of the house foundation wall. Then I could install a small gas fired furnace and registers through the wall. This plan would at least allow heat to blow across the floor at the room perimeters. Finally, I have thought of installing radiant heat in (or, rather ON) the floor. I don't mind losing a couple of inches in floor height but I just don't think that, as much as I would love to have warm a floor, this is a cost efficient system for this little house. They have good reflective underlayment's for this now days and they have an electric system as well as the hydronic but both would be expensive to install and the electric, I think, would be expensive to run....even with the co-op plan. So...after all this...what do YOU guys think? What's the best and most efficient way to heat this little place with its existing concrete floor??? And...THANKS for reading all this!
silverfox
designer/builder

[rabadger]

Do a load calculation for radaint heat. If you can put the right number of loops down determine if you can do a overpoor. This will give you warm floors and warm feet. At 440 sq ft with the proper insulation something as small as a 38,000 BTU water heater may do the trick.

But remember - proper planning will make or break a heating system design.

[Silverfox]

Thanks, Richard. I'm no HVAC guy so I will have to rely on other's to do the numbers. I have always wished I COULD do the numbers and calcs myself but it is an area that I have avoided for too long. I plan to have several different companies and the electric co-op come look at this little house and the heating problem. I would love to have radiant floor heat if it would be efficient. I have written to several radiant companies for their opinions as well. The one company that has peaked my interest the most is Radiantec. If you are not familiar with them I hope you will take a look at their site and see their research and system. They, as you have suggested as a possibility, have developed a water heater system that can also be supplemented by solar if you want that option down the line. It is decidedly cheaper than going the boiler route although it isn't as cheap as buying a gas furnace or installing the fluid electric baseboards. My main concern is to live cheap on a monthly basis. But a close second is to have a warm floor in the house if possible. Radiantec's system relies on a gas fired water heater so that leaves out the duel-fuel plan that the local electric co-op has. Radiantec pushes a condensing unit ONLY for their system. I read all of their site literature yesterday, there is a lot of it, and was fairly impressed with the logic of their system. The hot water heater they push is called the "Polaris" and goes off at around $3200 and change if I recall correctly. :( Seems to me, though...after reading all of their pitch and research...that a guy could do his own system for less money. I appreciate your answer because I would love to have radiant in the floor. I was thinking, like you, that since this house is so small it could be a possibility with a hot water heater system. Have you ever done one? What do you mean by..."If you can put the right number of loops down determine if you can do a overpoor"? I would THINK, since it is a slab already, that an inch and a half float of lightweight would be no problem. I don't know what you mean about the loop number though? Thanks again, I will keep you posted on the events. Trouble is...I haven't closed on the house yet and getting people in it to make suggestions and bids may take awhile. I'm anxious to get started but I'm sure you know how long all that red tape stuff takes to get a house sale closed. :rolleyes:
Silverfox
designer/builder

[rabadger]

It's easy, they do it all the time with standard hot water heaters. Up to around 1500 square feet of garage and basement (in cold areas of the country). For only 400 square feet I would try to use a water to water heat exchanger and water heater. That way you have hot water and radaint in one water heater.

[Silverfox]

Thanks again, Richard. So you are recommending an Indirect System where the hot water and heating are separate and use a heat exchanger. Radiantec seems to like the Direct System where you don't need or use a heat exchanger. I guess that's why they use the Polaris water heater...it's 95%plus efficient. Maybe they recommend the direct system because it's cheaper without the heat exchanger. I do like the simplicity of the Direct System...everything just flows from the water heater to whatever is calling it, no need for the exchanger or anti-freeze and it's cheaper. Since I know nothing about radiant heat it is interesting to me that Radiantec likes the Direct and you like the Indirect. I would go with whatever is the cheapest to run I suppose. Any reason you specified the Indirect method in your previous post? I'd like to learn everything I can about the subject.
The other thing that bother's me about this project is that I don't know if the slab was insulated from underneath? I'm wondering if I should put down some ply on top of the slab before I put the tubes down? There is a company that makes a renovation board out of green ply that is grooved for the tubes. I like it but the tubes in this system are only 3/8". I would like to have larger tubes than that. Another thought I had was to put down that ply with styro sandwiched in the middle of it and then the tubes on top of that. My thinking is that if the slab is not insulated it would use a LOT of energy to keep it heated as a maas. I think you would lose heat into the ground and the cold ground would continue to try and keep the concrete cold and suck up the heat. If I am wrong about that then it would be cheaper and easier if I didn't have to put an underlayment on top of the slab.

[rabadger]

Thanks again, Richard. So you are recommending an Indirect System

I am not recommending anything. There are several ways of doing it. Get someone that knows how to do it correctly to look out for you and is not looking to sell you a product. Thats how you will learn how to do it.

The number of loops needed is determined by the required BTU needed, water temp, and GPM. First is the load calculations and design, then put down the insulation, tubing, then poor light weight concrete.

You also have to figure the resistance in heat flow from the heated floor into the room via carpet, stone, hardwood floor, etc (the finish floor material)

[Silverfox]

Got it. Thanks a lot for your help, Richard. Much appreciated. Thanks to you I now have a plan of action.
SF

[zkt]

"Trouble is...it has a concrete block foundation with a concrete slab for the floor. You can see the slab sitting on top of the block foundation outside the house below where the siding stops."

If I understand correctly, you have a suspended concrete slab floor. Quite possible as 20x20 ft or so. If you can come up with a way to insulate that mother you will have a fine heat sink for radiant floor heat. The maximum loss in room heigth is limited by how you fasten the tubing down. Interesting...Good luck

[handyman4life]

According to me you have a suspended concrete slab. You need to determine the number of loops needed by the required BTU needed, water temp, and GPM.

[Richard A Hetzel]

Radiant heat will not work very well, because you will be unable to place insulation below the concrete floor, or at the edges of the slab, so the heat loss to the earth will be enormous, especially in such a tiny building. Efficiency will ne bad to poor at best. It will be difficult to beat electric heat for efficiency, because its efficiency is usually 100%...ALL the electric used creates heat. You would be better served to insulate everything as much as possible, and painstakingly seal every source of drafts, and stay with the electric heat. How much of your 440 square feet are you willing to devote to an equipment room for a boiler and manifold? Electric heat uses no space.