Sunday, October 23, 2011

Digging A Hole To Save Energy

Here it is on a sunny day as the dust slowly settled.

It began with  this job listed on our energy audit:

78.0 points

4 Stars

2.5 pts, 1 step
Install R-25 rigid foam board to interior or exterior side of wall. Does not include cost of coverings.

Location - Below- (part or all) Grade Wall: Garage masonry, West + North

[I'm reading this laughing because there were several different recommendations about the garage masonry and I see this says R-25, but the others say R-30 and that's what I ended up doing.]

We had the audit at the end of last December.  You have 18 months to complete as much as you can to get a rebate from the state on the work done.  The limit is $10,000, but in our case, since we are starting from an initial rating of 3 Stars plus, our maximum rebate is $7,500.  We didn't feel much pressure.  We went to an Alaska Housing workshop, which we thought was going to tell us how to read the audit chart.  We should have read the notice better.  It was about heating.  It was well done and we learned a lot, but heating was not on our recommendation list.  But they got us to the right place - the Research Information Center at Boniface and Tudor - for the workshop on how to read the audit report.  (All the workshops are free and held frequently, see the links.)

So, I decided to do the garage walls, lower part, which are uninsulated cinderblock.  The choice was interior or exterior.  We went to the insulation workshop.  It wasn't nearly as good as the heating workshop and while it pointed out issues for me, it didn't answer the questions.  But I did decide that since R30 means 6 inches of board, that would take up a lot of space inside, I would do the exterior for the west wall.  We don't go to that side of the house much and there was a long neglected flower bed and a cement path.  (The path is so covered by old leaves and soil you can only see parts of it.)

So I started to dig.  But I still had questions.  Which foam boards should I use?  What adhesive did I need to glue them together?  Against the house?  How deep did I need to go?
I looked on line but couldn't find my specific answers.  I called the Alaska Housing Authority, but they just recommended more websites.  The sites may have had the answers, but I couldn't find them.  I went to Lowe's to see my options.

This board is R-3.9 per inch, so it would need 7 or 8 inches (and boards) to get to R-30.  There was a blue board that was R-5 per inch. I asked about adhesive and the stockman pointed to this foam, but said this wasn't his expertise.

I had an email in to the energy audit rater and called a friend who'd done the same project a couple years back.  He said no glue - the dirt will hold the foam against the house.  And to get a metal cover.  He sent me to Combs Sheet Metal.  But I was going to hold off on that until I knew exactly what the measurements would be.

I took things easy.  No more than an hour a day so as to not mess up my back.  Actually, the digging was like going to the gym and it felt good.  But it took some time at that pace, but it also let me get more information.  The energy rater called me and added some foam on the bottom horizontally.  He said 2 feet, but I didn't have that kind of room, so we settled for 18".  And he suggested 6mil plastic for vapor barrier.  I'd thought some sort of plastic cover between the boards and the dirt was a good idea already.

I decided to check out Home Depot and the prices were about the same as Lowe's and so I got my foam there.  This was R-5 per inch in 2" boards.  The trusty van had room for it all. 

You can see time passing - now there are leaves on the ground.  But the hole is getting deeper.   In the third picture, the horizontal foam is on the bottom - with some dirt on top - and the vertical foam against the wall.  I was starting to have trouble on one end with cave-ins as I dug.  But the foam was down and it was time to work on the 6" foam against the walls.  Lots of measuring and cutting.

The 10/21 shot has the metal cover on it.  That was amazingly easy to arrange.  They just needed to know the dimensions and the color and it was ready the next day.  I have no idea what it should cost, but at $160 didn't seem that much.  But what do I know about sheet metal prices?  Nothing.

In this picture you can see the first panel.  I got the 2 feet X 8 feet X 2 inch panels.  But the hole was 35 inches deep after the horizontal panel went on the bottom.  So I wrapped up three panels here and then I had to cut the others to go on top to fit to the edge of the siding.

Here I've got all the panels - two 8 foot packages of 3 and one 7 footer.  Then on top of those the same thing but only 12 inches instead of 24.  And this picture has one of the pieces of metal to cover it.  There's a lip that goes under the siding.  They come in 10 foot sheets, so I had two of those and this smaller one for the middle.

Now all that is left is to fill in the dirt.  And it hasn't snowed yet.  I got a fair amount in yesterday.  I think I'll just fill it up to where the metal goes and then in the spring I will add some compost and manure.  The sun's just come out so I'll go out and finish this off.  I'll add the pictures to here later.

So now I've got to do other things on the energy rater's list. This was the west wall of the garage, and I still have the north or back wall of the garage. I'll do that on the interior side because it's much harder to dig in that   part of the yard.  And now that I've read more carefully, I only needed 25R, so it won't take up as much room - 5, not 6 inches. And the front is two small panels that I might just do inside as well. They'll be relatively easy. And then there are other things to get us up to the next level.

It's nice to do something you've never done before and get past the obstacles of ignorance.  The only hangups were knowing what I needed to do and what stuff I needed to buy.  And this should save us a little on heating costs and certainly pay for the materials in a couple of years.  And I have a much better understanding of how all this works now.  And I'm pumped to do other projects around the house I have no idea how to do.

UPDATE 9:40pm:  Here's what it looked like when I finished today.  I might leave it like this until spring when I'll put in some compost and manure or maybe I'll even do that now if there's enough time before it snows.


  1. Since I live in the desert, reading this was like hearing about life on the moon.

  2. Desert dweller, are you talking about needing the insulation to keep out the cold? It would seem to me in the desert you need to do the same thing to keep out the heat. Or were you referring to the general difference in climate and vegetation?

  3. You must have continuity in the other façades...


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