Cut my heating bill by 39%

[TimJFowler]

Woo Hoo!

I received the first full heating bill since insulating our attic to R-50. So, I ran the numbers and compared Therms of Natural Gas used per Heating Degree Day from Jan/Feb 2009 with R-50 insulation and Jan/Feb 2008 with very poor insulation. The result - 39% less Therms per Heating Degree Day used!

I also did a rough break-even calc and we should hit break-even in 5.5 years or so (depending on natural gas prices of course). Not too shabby.

More info and calculations here: Heating Bill Before and After Attic Insulation | EcoNewMexico.com

Insulation - It's not just a good idea, it should be the law!

[Daox]

Thats very encouraging considering I too just did mine! I completely agree, more insulation should be code. We would save massive amounts of energy.

[SVOboy]

That's quite the cut! How did temperatures compare?

[TimJFowler]

I used Heating Degree Days* in the calculations so that I could directly compare the two bills.

Heating Bill Comparison
Before Attic Insulation:
Jan 14 - Feb 13, 2008 (31 days)
Natural Gas used - 121 Therms @ $141.72
Heating Degree Days - 1103
Therms per Heating Day - 0.1097

After Attic Insulation:
Jan 11 - Feb 10, 2009 (31 days)
Natural Gas used - 57 Therms @ $60.19
Heating Degree Days - 852
Therms per Heating Day - 0.0669

Natural Gas Use Difference .0669 / .1097 = 60.98%
~ 39% reduction in Natural Gas Heating Bill

* Heating Degree Days - the number of heating degrees in a day is defined as the difference between a reference value of 65°F (18°C) and the average outside temperature for that day.

[Higgy]

What did you do to make it R50 Tim? Did you post pictures in another thread? I can't remember now. If you didn't please post some.

[TimJFowler]

The short answer is I installed soffit baffles and sealed over the central hallway which was a huge thermal bypass. Then we had ~15" of cellulose blown in to the attic. I did take photos, but given how low the roof is, they aren't very exciting shots. But here is one -



The longer version of the story is here - Cellulose Insulated Attic Makes For a Cozy Home | EcoNewMexico.com

[jwxr7]

very good! Nice way of comparing too (using heating degree days).

[Daox]

What did you have for insulation up there before the cellulose?

[TimJFowler]

The original attic insulation (still in place) is old mineral wool (rock wool) blankets. Unfortunately, they were installed sloppily and had settled to 2-3 inches thick (I assume they were thicker initially). Whomever installed the insulation left gaps between batts, ran batts OVER wiring, and ran batts flush against the eave vents. I had to get creative to position some of the insulation trays up to the eave vents.

The biggest problem was the big thermal break created by the central hallway. The hot air supply duct runs down the central hallway in a channel created by dropping the hall ceiling about 6". This left the interior of both hall walls open to the attic and the duct itself was uninsulated. I sealed over the top with sheets of drywall cut to fit and then sealed in place with spray foam.

Doing all of the prep work in the attic was a big pain in the rear, but I noticed a difference in how often the furnace was running even before the insulation was blown in.

This was definitely a big project time-wise, but absolutely worth it.

Tim

[snotrawket]

say I had the exact same house and now that you have experience doing it I wanted to contract you to do it for me. What would be you're price (if you would just say no, what would you advise me to pay someone to be fair hehe)