Radiant installed directly under hardwood floor?

[Sawyer]

Has anyone had experience with solid hardwood flooring installed above the sub-floor with radiant tubing (1/2") running between furring strips (5/8")anchored to the sub-floor? I really hope to hear from someone who is having good results. I do not want to install the tubing in the joist area below the sheathing. I want to get the water closer to the hardwood so I can heat with lower temperature water so I can stretch the time between firings. I do plan to put foil down to reflect the heat upward. The area directly below this room is a heated den area.

I have been told not to exceed 85 degree surface temperature on the hardwood floor or I may have problems with cupping or warping, this was from a person who does not have hardwood installed in this manner. The hardwood was kiln dried and has been stored inside for 3 1/2 months and is well acclimated to a winter indoor climate.

I have low windows in the living room with lots of outlets, panel rads or radiators do not seem to fit this layout so radiant under hardwood it is.

George

 

[jimbom]

85 °F surface temperature limit may arise from a rule of thumb to insure the floor remains comfortable for occupants. I designed my heating load to be able to stay below 85 and still provide the necessary heat.

Wood does move in response to temperature and moisture. IMO the range of temperature and moisture is the important factor, not any specific single temperature.

 

[in hot water]

Do you know how many BTU/ square foot you need? Is it just floor warming, or do you want to heat the room? The above floor installation methods can safely produce 15- 18 BTU/ ft IMO.

Ideally would want a conductive transfer where the tube is installed in aluminum heat transfer channels. Then the hardwood is in direct contact with the aluminum.

The system you are considering basically heats the air space and transfers most energy by convection. The aluminum below will reflect some of the radiant energy also.

Keep the aluminum clean if possible. Even a thin layer of dust really lessens the radiant reflection.

I have installed several of these Watts Radiant above floor jobs. The condos had forced air heat also, which was needed on design days as the floor would not cover the load. Furniture and throw rugs will reduce the output also.

One thing to consider is the tube will squirm around as it heats and cools. Plan on some attachments every 2 feet or so or you will hear that tube movement. Also consider pex al pex tube, it does not expand and contract as much as plain pex. minimize temperature swings also to keep the wood happy and lessen the expansion movement. outdoor reset controls are nice for these dry systems.

Correct, it is best to let the flooring acclimate to the conditions where it will be installed. Hardwood moves due to change in humidity levels, not heat necessarily.

In one case a hardwood flooring job was installed on the coast of Maine. with the doors open and the moisture rolling thru, the flooring actually expanded enough to push the bottom wall plates on the sub-floor. So try to keep the humidity constant if possible.

www.launstein.com has some excellent info dealing with hardwood over radiant

hr

 

[Sawyer]

The room is presently forced air heat via the coil in the air handler. The living room has lots of glass so when the kitchen and front half of the house (we have two zones on the ductwork) the living room is normally four degrees cooler. I can live with 15 BTU/ft and I can go with eight inch spacing. The room is 20’x28’=560 sq./ft.

I have a friend that has a staple machine and staples, he will drop that off for me to use. I will look into the transfer plates. I was unaware of their existence for above floor application.

I am planning to use a Tekmar thermostat and sensor rather than wall mount. I really like the Tekmar now that I have it installed in the workshop floor. I set the slab temperature and it stays +/- 1*.

We also have a whole house humidifier on the air handler and A/C for summer, high humidity periods.

I will go to http://www.launstein.com and read. One have to be careful what he reads for facts, I appreciate a recommended site.

 

[kuribo]

A lot depends on the species and dimensions of the wood you lay down. Narrow is better than wide planks. If you use oak, quarter sawn in best. Usually the 3/4" thick US species are not the best...there are thinner exotics (ipe comes to mind) that are extremely stable and are much better suited to hydronic heat.

 

[Karl_northwind]

you might look at smith environmental products. they have some snazzy high output low temp fin tube radiators. google them. they're available from at least one distributor in wi.
karl

 

[Sawyer]

A lot depends on the species and dimensions of the wood you lay down. Narrow is better than wide planks. If you use oak, quarter sawn in best. Usually the 3/4" thick US species are not the best...there are thinner exotics (ipe comes to mind) that are extremely stable and are much better suited to hydronic heat.

Unfortunately I have to use the yellow birch flooring that I have in the house. It is going to be a random 3-4-5-6.75 inch pattern. The lumber was cut from straight, high quality logs.

 

[Sawyer]

you might look at smith environmental products. they have some snazzy high output low temp fin tube radiators. google them. they're available from at least one distributor in wi.
karl

Thanks Karl, I looked at their site and the radiators look worth investigating. Hard to believe that they can heat with that low of a temperature.

Do you or someone you know, have experience using this product?