Better Insulated Headers – by Ed Minch, Energy Services Group
Wood is a poor insulator, with an R-value of about R-1 per inch. This means that a double header over a window or door has only an R-3, but our walls are much higher. Here are a few ideas to give headers a boost.
First – don’t install headers where they are not needed. Your engineer will be able to eliminate headers in non-load bearing walls. This will save energy and cost you less to build.
In either a 2X4 or 2X6 wall, you can move both headers to the outside so they are touching each other, then install rigid board on the inside – a piece of 1/2″ board will add about an R-3 in a 2X4 wall, and 2-1/2″ of board will add about R-14 in a 2X6 wall. With the 2×6 wall, you can also use fiberglass batting at about an R-9.
If you use I-Joists for headers, you can fill in on the inside and outside surfaces and between them with even more foam board or fiberglass. Filled with foam board you will get about R-16 in a 2X4 wall and R-30 in a 2X6 wall.
Your engineer can give you a header sized so that you need only one piece of 2X material – it will be taller, but in many cases there is plenty of extra height for this. A single header will give you the most space for added insulation, and lower your construction costs a little.
Whatever material you use, pay attention to a tight fit for best effectiveness.