We're building a new house (probably ICF foundation, SIP walls/roof) in the Adirondack Mountains of NY (near Lake Placid).  The house will be 2 floors, basement and main living floor with a 48 foot  side facing south.  This wall will have a 16 foot slding glass door in the center (living room) and 6 foot sliding glass doors to either side (bed room on one side, office on the other) for passive solar gain.  The south wall faces the woods which are about 60 feet away and those trees are mostly 60 foot tall deciduous varieties (i.e. they lose their leaves). 

The architect is recommending a concrete floor under the main floor for thermal mass (both for the heating system and for the passive solar gain).  He suggested staining the concrete to look like tile or actually tiling the floor and using area rugs sparingly. 

I go round and round about this concrete floor idea.  It is more expensive to install than a traditional wood subfloor (we can do the carpentry to install the wood subfloor ourselves....the concrete will have to get subbed out).  However, we have been told the concrete is really integral to the radiant heat and to the passive solar.  It also sounds like the radiant heating system will run more efficiently in a concrete floor, compared to a radiant system under a wood subfloor.  However, I am nervous about the hardness of the concrete.

Does anyone have any good information, statistical or anecdotal) to help me make an informed decision about this?  I am concerned about the upfront cost VS the cost of running a radiant system using the 2 different floor types,  the differences in efficiency, the reality of passive solar gain in such a northern climate and how comfortable the concrete might or might not be.

Thanks in advance.  Cathy

We live in a home with radiant in concrete. We will soon be building a new home that will be solar with radiant in a slab.

Concrete slabs are harder on the legs. You need to wear good shoes when doing alot od walking in the house. The energy savings and comfort from a radiant solar slab is wirth every penny.

Warm concrete floors on a cold winter morning are heaven. I also find the warmer feet, cooler head very good for concentration. We keep the heat several defrees cooler than we would with other systems.

It is your house: get what you want.

Passive solar is great until it’s not passive anymore (wide temperature swings). I would specify a "sandwich radiant system" or perhaps gypsum based over pour and an engineered wood floor atop. If you are building slab on grade great, if you have a suspended floor, pouring concrete is rarely cost effective. When it comes to education, there is no substitute for experience.

MA

There is no way my wife would let me get away with a concrete floor for the kitchen. No way I would want to walk around on it either.
I know people who are doing radiant hydro with wooden subfloor and a gypcrete poured on top of the subfloor with the pipes encased in the gypcrete.
There are also wooden subfloor products which come pre-routed for the pex pipe and then flooring goes on top of that. I understand that the gypcrete over pour can actually be cheaper though.

Radiant IN the slab can be a blessing and curse. If you don't mind one temperature all the time, it's the best and is very efficient if it's constructed correctly for our upstate weather patterns. If you like it warm while you're awake but cool when you sleep, expect alot of sleepless nights. When you use the slab as storage, you won't have the variable choice in temps as you would with radiant above the slab.

Warmsmeup,

 

That is what zoning is for. Keep your bed room cooler than the other areas. Zoning can also be an energy saver. Shut down rooms not in use, begin heating them a few days befor your guests arrive. Forced air systems don't like being shut down to 50%. Ducts whistle.

Jill,

Tell us about how your Solar/Radiant will work. Maybe start a new thread?

Patrick T

Zoning is a given. But as I said, slab heating is still an impractical design for everyday living when you desire temperature differentials through the day.

I am going to assume that you base that above on the habit of turning down the heat while away for the day to save money.

Our SIP home with radiant floor heating in a concrete floor does not lose enough heat during the day to have the heat turn on. Our heating system usually only turns on in the middle of the night for a few hours. The exception to this is when the outside temp is consistently 10 below or colder.

Our bedrooms are are on a different zone and because we like it at 63-64 for sleeping, the heat in there never turns on unless it is very cold outside. The radiant system does feed through our bathroom floor, so that is always toasty warm first thing in the morning.

In our new home,  will be better solar sited to catch all the heat we can during the day and will also have a solar hot water system to lower the costs for the heating the radiant floor heat.

We have found that the concrete floors and  radiant heating combined with a well insulated home  operate very differntly that the normal North American home where the heat cycles on and off all the time.

Thanks for all of the input thus far. 

Jill:  Can I ask where you live?  At least roughly?

What did you do to finish your concrete floor?  Stain? Tile? Manufactured wood? Floating wood?  Do you use area carpets? 

Also, how long have you been in your SIP house and how have the SIP panels worked out for you?  Perhpas this should be another thread in the SIP forum but it is a huge concern of my husband's.  He doesn't really trust the longevity of the SIP systems.

I am not worried about too much/out of control solar gain.  I am more concerned that our site and geographical location is such that we really don't have enough consistent solar gain to warrant the concrete floor.  However, it sounds like the concrete will maximize the radiant heating set up and minimize our energy output, which is the point.  BTW, in our area we don't have access to gypcrete or anything along those lines so it will be a conventional pour over 16 inch 4X2 trusses (24" OC) topped with either 3/4" structural I decking or 9/16" steel decking.

We are not interested in our interior temperatures being adjusted during the day.  I know radiant heat is slow to respond.  We would zone like Jill with a chilly bedroom for sleeping and a reasonably warm house elsewhere.  Our house will not be that large.....less than 1800 sq feet for the main living area, plus a basement.

Cathy

Ours is 2" of concrete on a plywood deck( beefed up joists to handle the weight) We did all the radiant ourselves. had the floor poured. We acid stained it ourselves( well my husband did). We have a crawl space in this home.

We use area rugs, but could have added wood or tile etc. if we prepared for it. I like the acid stain, just like tile and super easy to clean. We have dogs , cats and horses and are in and out with muddy boots. I never worry about the floor being damaged.

We live in Star Valley Wyoming. Lots of snow and cold. Hot summer days but ususally cooler nights.
Eight years in the SIP home. As long as all the proper roofing and siding procedures are done. There are no problems with SIPs. We will use them again. We have one piece of SIP that has been sitting outside uncovered since we built. It sits in the rain and snow and heat and is still in very good shape.
We will go with a larger slab because we aim for solar gain and more storage. The concrete really levels out the temp and also keeps it cool in summer( with proper solar shading).

You do need good shoes for alot of indoor walking but your legs get use to it. The tradeoff is more than worth it in comfort. Combine the slab with the Sips and you will never go back to old heating systems.

We do have a propane stove(fireplace) for quick heat when during the shoulder seasons but very seldom use it, maybe once a year for an hour or so.

It sounds like very similar situations.  We too will have a wood stove for the shoulder seasons.  We have a lot of wood we cut when we cleared the lot. 

You are the second person I've heard of who has stained the concrete floor themselves.  I was about to give up on the concrete floor but you are re-inspiring me. 

As for the SIP, did you do a SIP roof?  What did you use over the SIP?  Meaning, between the SIP and the roofing?  And what type of roofing?  Are your SIP with OSB?

Now if I could convince my husband to add the horses to the project I would be in heaven! 

Thanks for your reply.  Cathy

OSB SIP roof, water and ice shield, metal roof.

Staining the concrete is very easy, just do lots of research. We ended up with a wonderful cheap floor. Our home is 1200 sq feet( one floor).

We had the shell erected and did all the interior work ourselves.