In Floor Radiant Heat

[coldinmn]

I've been told by a builder that a whole house in-floor radiant heat system does not qualify as a primary system, and requires a back-up (e.g. forced-air furnace). Is this really code requirement in Minnesota, or am I being misguided?
Thanks in advance for any clarifications on this subject.

[ralphtheplumber]

What exactly do you mean by a "primary system"?

The in-floor should be more than capable of heating your house, assuming it's reasonably well-built. You can run into situations (poor windows, no insulation) where the heat load of the house is so great that the floors have to operate at an uncomfortably high temperature to keep up.. is this what he means?

[Green Mountain]

Around here everyone is a heating engineer. I have seen so many heating "trends" it isn't funny. Now the golden haired boy is in-floor radiant heat.

If you are talking about a middle income ranch house you can be comfortable with in floor radiant as a primary source of heat, Maybe. But around here folks are building 1M ski vacation homes. Some plumber will sell them on in-floor radiant. Bad move.

Situation. Folks live in New York City, they decide to go sking for the weekend. Walk in the house on Friday night. Sometime on Saturday the house comes up to temperature. If the house is on a southern exposure then by Saturday after noon they are opening the windows to cool the joint down.

If you want to have in-floor radiant to keep your tootsies warm that is fine. But put in a hydro air system also to heat the air.

Sorry, Ralphie about the plumber's crack.:D

[ralphtheplumber]

Some plumber will sell them on in-floor radiant. Bad move.
I think this comment might be directed at me.. :mad:

Are you talking about a concrete slab here, beenie? 'cause those take a while to heat up. Warmboard can get there in 20-30 minutes.

[coldinmn]

Sounds strange doesn't it? Thats why I thought I'd get opinions here.

No, from what I interpret, he's saying that there's some sort of code that requires installation of a system to backup the radiant heat system, and not just for fresh-air exchange. We're contemplating a highly efficient TF/SIP house and thought radiant heat would be ideal. But not if we also have to install another whole system as well.

Thanks!

[Green Mountain]

I think this comment might be directed at me.. :mad:

Are you talking about a concrete slab here, beenie? 'cause those take a while to heat up. Warmboard can get there in 20-30 minutes.


That's why I said "some" Plumber not one who is as well versed in heat transfer such as your self. :o

[Green Mountain]

Sounds strange doesn't it? Thats why I thought I'd get opinions here.

No, from what I interpret, he's saying that there's some sort of code that requires installation of a system to backup the radiant heat system, and not just for fresh-air exchange. We're contemplating a highly efficient TF/SIP house and thought radiant heat would be ideal. But not if we also have to install another whole system as well.

Thanks!

Let me ask you this. Were you thinking about installing cooling as well? If so I would diffinately put in a hydro air system as well.

I don't know of any code that saids you must have 2 systems in your home. If I were building new I would have both systems. If your living space is on a slab I diffinately would have infloor radiant in it.

[ralphtheplumber]

there's some sort of code that requires installation of a system to backup the radiant heat system
I have never heard of such a thing. You wouldn't happen to know which code or section he's referring to here.. ?


But not if we also have to install another whole system as well.
Since you mentioned fresh air, is it safe to assume that this house is going to have an air handler and some duct? If you've got that, it's not a big deal to add a hot water coil and another zone valve.

[coldinmn]

Thanks, I see that I should consult with experts in the field before we go down the road much further. As far as heating/cooling/fresh-air goes, whats your general opinion of the high-velocity systems.

[bluestone]

Sounds strange doesn't it? Thats why I thought I'd get opinions here.

No, from what I interpret, he's saying that there's some sort of code that requires installation of a system to backup the radiant heat system, and not just for fresh-air exchange. We're contemplating a highly efficient TF/SIP house and thought radiant heat would be ideal. But not if we also have to install another whole system as well.

Thanks!

That's just "nuts"

[bluestone]

Coldinmn, gave the short answer before. Now let me try the long version.

I've been timber framing in Vermont for nearly 30 yrs, since '80. In my opinion a SIP sheathed timber frame in your location is the ideal candidate for infloor radiant, as a matter of fact it is that very home I live in.

With that being said, Benncool's warning is not without merit. There is a large thermal flywheel effect in these homes, you do not want to setback heat on a daily basis, there's just too much mass in timbers and the panels, once the house reaches equillibrium, you've achieved the most efficiant heating state.

That is not to say, if the house is a vacation home you should not set it back when you are not there, but for various reasons I feel the setback should never be less than 60F. Here's why Sips have a pretty large co-efficiant of expansion, and stuctural issues are a concern, popped siding, drywall, and edge sealing to name a few.

Of more concern comfort wise would be, how do we address that heat flywheel when we come up for the weekend ( if this is to be a permanent home this is moot)? One way is to install controls that allow you to remotely raise the T-stat setting ( of those 1mil $ homes Benncool was refering to I know of many where this is done. These controls are also good because the can relay the status of the home to you remotely ( too hot, too cool, freeze ups and such).

One final word, if this is going to be a primary home, look into thin slab radiant applications. My home is done this way, and I will say the heating is invisible, you don't hear it, you don't feel temp swings, you can't tell it's there, and in my home this is accomplished useing the most basic of controls. Honeywell T87's, max temp swing is about 1.5F, imperceptable.

Please dont forget about IAQ, you will need an ERV.
I can elaborate further, just ask

[tinknocker service tech]

If infloor is installed correctly and set up correctly it will heat any house quite well. As raulph the plumber has said.

if they want back up then run a loop of base board arround with a two stage t stat. base board as second stage.

i have worked on houses on the ocean here in jersey and even with a noeaster they have no problem with keeping up

Infloor is nothing new. Has been arround for many years. It is just more popular now

[Midwest]

Look for a HVAC sub who is familiar with radiant and can show you case history of their work. The quote you are being given about needing supplemental heating is innacurate, unless 10,000 lakes state has some unusual codes going on there. TF's are an excellent ICF & I assume your SIP's will be R-Control, since there is a marriage between many of their sales & manufacturing companies. Good choices in products, albeit I thought you would run into more resistance with using these building systems instead of with the radiant heating. Most contractors have little patience for 'new fangled' building systems, even though SIP's have been with us since 1952.

[markwolf]

I cannot tell you about the code in minesota but here is a very high scale home that I personally installed infloor tube heat in.there is only one munchkin boiler for heat & hot water.There are two independant spacepak cooling only air handlers for ac only.saying that infloor cannot be used for a primary heat source is just wrong! http://www.monolithic.com/gallery/homes/stitt/index.html I would shop around for contractors.

[markwolf]

Oh I forgot to mention the erv for fresh air requirements.

[Wdrake]

I am enclosing our screened in porch and would like to use in-floor heat. I am limited on space under the floor for insulation. I have laid down the 6mil plastic for moisture and am using the 2" blue board all the way around the perimater of the deck. Then was planning on using the same 2" blue board in each joist space topped by the silver reflective "bubble wrap" style insulation. I would then install the tubing above that, below the sub floor. I am located in upstate NY and our winters get chilly is this the proper way to insulate? Should i use 1/2" or 3/4" pex? The rest of the walls and ceiling will have plenty of insulation but just concerned with the floor. It will be a non vented crawl space.