Wednesday, June 11, 2008

An Easy way to make your Home more Energy Efficient

Chalk up another fun project completed. This past weekend I installed a reflective insulating material on the inside of my double garage door. The door faces West, so it receives a lot of direct sunlight in the afternoon, plus there is indirect reflection from the concrete driveway.

Because I wanted to reduce the radiant heat transfer through the door, I chose a foil based, reflecting bubble material. The idea is to reflect the heat as opposed to sealing or simply insulating the door.

I found just the right material at Home Depot called Reflectix®. A lot of folks get hung up on R-values, but in this application R-value is not the driver. The Reflectix® website provides a good explanation comparing the foam insulation of a styrofoam cup to that of a glass-lined thermos. The foam cup has a higher R-value than the thermos lining, but the internal surface of the thermos reflects the heat or cold from the liquid back inside the thermos keeping the liquid much warmer or colder than the cup. Think about it, would you rather drink coffee from a thermos jug or a foam cup hours later?

I bought three 25 foot x 24 inch rolls of the material at $21 each and had 10-12 feet left over that I plan to use later to wrap AC/heat ducts in the attic. I measured each door panel, cut the material to fit the length and cut the width to allow at least an inch and a half overlap on the top and bottom. I then tucked the top and bottom edges (overlap) into the channels of the door panels. The material stayed in place very well without any adhesive, but you could use a light dusting of spray 77, if desired.

The low emittance surface of the reflective insulation blocks up to 97% of the radiation. And I can definitely feel a difference in the temperature in the garage. I can only assume that this will help keep the house a little cooler as well. Especially since I have a doggy door between the wash room and the garage.

Is it worth it? How long will it take to recover the initial costs? It may take a year or two to recoup the costs, but it’s really irrelevant because it has already made the garage a lot more comfortable place to be in the summer time.

Because the material is reflective on both sides, I anticipate that in the winter time the warm air in the garage (warmer than the outside air temperature) will be reflected back into the garage keeping the area a skosh warmer. Along those same lines, I have also noticed that the heat from my vehicle when pulled into the garage with the door shut – heats up the garage more so than before! Exactly as one would expect, right?

I seem to have alleviated one problem only to be “foiled” by another. So now I leave the door open for a short time to let the vehicle cool or if the weather is nice I park in the driveway. I can rationalize that having the garage door up or down in the evening is not that big of a deal because by the time I arrive home on a typical work day, the sun has set below the tree line and is no longer impinging on the garage door.

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