Retrofitting Radiant Floor Heating

[homelessdespot]

Saw some videos on youtube that make it look easy but ... Does retrofitting radiant floor heat work out well in the existing 1st floor of houses with unfinished basements?

House shopping in the 1500-2000sqft range in the northeast and a lot of these old house have really old furnaces and some pretty disgusting old hot air systems with vents and returns on the floor.

Wondering if retrofitting radiant floor heat on the first floor is possible, efficient, and not astronomical in price. Alternatives could be new ducts off the ground or retrofitting hot water baseboard (allergies).

 

[mike93lx]

Absolutely possible. Not at all easy.

Trying to manage all that PEX without experience will make for a miserable time. Talk to some heating pros in your area. This will be expensive

 

[homelessdespot]

Oh, I definitely meant hiring a reputable company. Ah, so it would be a lot more expensive than running all new ducting?

 

[mike93lx]

Ducting can be very expensive. I doubt you will have a lot of people cross shopping those options, so I think it would be hard to tell.

 

[Jackfre]

First, is your current duct system properly done and would it pass a pressure test. Once you know that you know your benchmark. Retro-fitting proper duct work into a home is extremely difficult and yes costly. Staple-up ducting is certainly possible but it too is costly and must be properly done. Spend a bit of time on Uponor’s and Rehau’s web-sites to get the angle of the dangle. Your other option is mini splits.

 

[yeldogt]

What about AC ... properly done they do not kick up lots of dust. The new equipment is VS.

Anything is possible ... retro under floor is all dependent on needed output. Typically staple up is not enough BTU output ..plates are needed. Old brick or stone house -- still may not work. I have done panel radiators with ....

It's expensive

 

[Randy in Maine]

Another option would be to use radiators that are set up for condensing boilers for input temps of about 140ºF. Those are fairly new I think.

That being said I did retrofit radiant pex tubing under my wood floors using the metal plates and insulation under it in my 1200 square foot house with a crawlspace. It works OK, (but not as good as the radiant floor heat in the garage slab due to the large thermal mass) but we also have a supplemental heat source (a propane "woodstove") for when it gets cold out or we want to warm up the air from the 62º floor temps.

I do have pretty good sprayfoam insulation in the house which helps no matter what heat you are using.

If I have it to do over again, I would just do the radiators on that zone. About the same cost to install and operate. The heated floors really keep the heat down where you can feel it though (my ceilings are about 10º cooler than the floors) so it is kind of efficient.

 

[homelessdespot]

Thanks for the suggestions guys. I'll keep them in mind when house shopping.

 

[bmwpowere36m3]

Depends...

I'm in CT and we completely gutted/renovated our 1956 ranch. Ended up with:

• Lochinvar Mod/Con Boiler
• Indirect HW Tank
• Buderus Radiators (European style)
• Buderus Towel Rack and staple-up floor radiant (bathroom)

The system is quite efficient and runs a low temps (ODR curve), but required "oversizing" radiators. Additionally added a staple-up loop in the master bath for floor heating.

Staple-up will require higher temps due to amount of subflooring (resistance) and needs to be insulated from below. Best approach is to incorporate plates (increase heat transfer).

First, I'd start with a good heat loss calculation including a blower door test. That'll keep you from oversizing your boiler (biggest inefficiency) and let you fix the biggest heatloss factor, infiltration. Then you can determine how many BTUs you need in each room and whether you have enough floor sqft and what temps you might need to run.

I spent a good while figuring it out. Final note, warm floors are nice. However in a well insulated house, with a properly designed radiant system, with enough floor coverage... the actual floor temps are not warm. Not the toasty floor you might be thinking of.

 

[Ak Jim]

Final note, warm floors are nice. However in a well insulated house, with a properly designed radiant system, with enough floor coverage... the actual floor temps are not warm. Not the toasty floor you might be thinking of.

This is the truth. The better the insulation and air barrier the lower the floor temp!

 

[75gmck25]

Another more complicated/expensive option is to replace the existing wood underlayment with the type that has channels for PEX. There is one company that sells 1 1/4" underlayment that has the channels and reflectors built into it, so you just run the PEX through it. Its expensive compared to running the PEX under the floor, but should be very effective.

Bruce