insulation?

John Abbott

Alan please see my Help post of today it gives a bit more info on the problem.Ypur insight would be appreciated.

John

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John Abbott

Air space?


















insulation beneath floor with radiant heat

Responses:
insulation under floor with radiant heat Lance Macey 08/01/09


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Date: August 01, 2009 03:06 PM
Author: Lance Macey
Subject: insullation under floor with radiant heat



I have true radiant heat installed beneath my 4 inch width white oak floor. The system consists of plates nailed directly to the subfloor with the pex tubing snapped into the plates. My heating contractor's goal is to run as low a temperature water throught the system as possible to heat the floor and not cause cupping and crowning that can result from over heating and drying out the wood. The basement environment is an unheated (New England cold) crawl space. The question is: with icynene foam insulation in place, am I better off with the spaces between the floor joists being completely filled so that the foam is in direct contact with the radiant tubes and plates OR is it more effecient to have a 2 inch air space between the radiant system and the foam insulation? No one seems to be able to answer this question with a good thermodynamic explanation. Does it depend upon the heat absorption characteristics of the foam? Is one way better than the other? Thank you for your help

Alan(OnVacationInOregon)Forbes

With plates,

heating is done by conduction and the entire joist bay should be filled with insulation. Without plates, heating is done by convection and you need an air space, i.e the top 2-3 inches of the joist bay should not be insulated.