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over our heads
wanting to use radiant heat

Our 1900 house had an old boiler system (I think it was water, but couldn't promise) anyway, the boiler itself was rusted out so we got rid of it but kept the radiators for the look. Meanwhile I've been investigating alternatives to the traditional boiler heat system such as using Pex tubing to provise radiant heat all over the first floor. Our house has the original hardwoods throughout, so a couple of estimators have said that we couldn't use this type of heat w/ our floors. However, I have seen other on-line posts accompanied to this site stating to the contrary. Any thoughts who is correct? And suggestions?


No estimator or contractor can truly anwser the question without calculating a proper heat loss and radiant design of the home.

Other factors a pro in the radiant field looks at is the r-value of the existing subfloor and finished floor as well as the joist bay centers.

If we can provide the proper btu's per square foot to every rooms floor surface to overcome the heat loss based on the floors
R-Value then dependent on the water temp needed we can ascertain whether radiant heat is a viable and cost effective option.

Another option is to keep the radiators, add thermostatic valves, pipe them in 3/8" pex via a radiant manifold and run the systems using a variable speed ecm circulator on constant circulation.

Piping would be just like page 19 of the link which is showing panel rads.


This is also a nice read for those that want to learn about zoning hydronic heating systems.

Re: wanting to use radiant heat

hardwood flooring and radiant dont mix,, it will dry out the wood far too much and it will create gaps no if and or buts.

the other factors are, its much harder labour wise to install radiant between joists as opposed to laying it on the subfloor. tile or engineered hardwood can be installed though

if the radiant is on top of the subfloor you will need to do a 1.5" concrete overpour. adding this much concrete you will run into the question of can your floor system handle this additional weight or will it need to be beefed up.

for retrofits, using the wire coil infloor heat is much quicker and adds very little weight to the floor as is electric however still needs to be covered in a layer of thinset to smooth out the floor

Radiant and Harrdwood

I disagree concering radiant with wood floors. You most certainly can install radiant with wood flooring. Floor shrinkage and buckling begin to occur when you floor surface temperatures get into the 80 degree range.

A good radiant designer will never desgin a system with surface floor temps that high. Most of the time the general floor surface temp falls into 73 and 77 degree range.

The installation also plays a factor. If using a good extruded plate system you get pretty close the same outputs at the same water temps as an dry over the floor system. A light weight overpour system tends to give you lower water temps but your surface temps don't change much at all.

While yes labor is a factor in cost the main difference between the two types of system from a design point is water temp which is dictated by the r-value of the floor surface. A 3/4" subfloor with 3/4" Oak has an R-Value of 1.68 no matter if you have concerete underneath it or your using a plate in a joist application.

For more on radiant and hardwoods please read


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