Radiant heat in an ICF home

Phil_5

I am building an addition to my house that is as big as the original house. The existing house has oil fired hot water base board. I would like to install radiant heat in the new part. Was going to use wood flooring through out the addition with tile in the bathrooms.Was thinking of putting sleepers down over the plywood subfloor,running the tube between the sleepers, filling up the void between the sleepers with concrete and addig the wood floors on top of the sleepers.The thought behind the concrete is for thermal mass to radiate the heat as gentle as possible thru the wood floors with no hot spots.Would like the system to be as efficent as possible. Would like to have thermostats in each room. I have experiance installing simple radiant systems and would like to try "something different" in my own house.Any body with interesting thoughts or ideas????

Mike T., Swampeast MO

Not quite the norm

Since you want thermostatic control in each room, why not use FHV-R room temp controllers (Danfoss) or similar? Do a careful heat loss for each space and vary tube spacing/diameter as heat loss and desired temp dictate; i.e. baths a bit warmer, BRs a bit cooler. The FHV-Rs will allow greater variance in the length of the loops as they will self-compensate for different pressure drops in different loop lengths--within reason of course. Use a simple reverse-return manifold and a single circulator with a differential pressure bypass around the boiler for times that all of the valves might be closed. Calculate your heat loss curve accurately, use reset and you will have an extremely efficient system.

Like any radiant system of higher mass, don't expect to be able to make extremely rapid changes in temperature, but do expect to be able to keep different spaces at quite different temperatures.

Since you'll need a new boiler consider a new one for the addition only. That way you can use a condensing model to its best advantage. It won't need a regular flue, just an accessible drain for the condensate and PVC out the wall. If you use a single boiler for both the radiant and the baseboard, you might as well use a non-condensing boiler and you'll have to take measures to produce two widely varying temperatures while protecting the boiler from low return temps (and possibly low flow).

Make certain your floor structure can handle the added dead load of the concrete!!! 1 1/2" thick concrete will weigh in at about 18 pounds per square foot--I'd use 20# sq/ft additional dead load for calculation.

TJ

Consider ICF floors

Have you considered using any of the ICF structural flooring systems on the market? Their kind of pricey, but your building for the long haul. Check out the LiteDeck web site. I used the lite-deck product for both floors of my house with radiant floor heating and the temperature in the house doesn't vary by more than 2 degree's between night and day.