Friday, November 19, 2010

Return Audit Results

After completing the work for the 2010 Home Energy Savings Program, we had our house audited again.

See related blog ( for initial FLIR photos and discussion. Since the original audit we undertook a number of retrofits as discussed in related blogs,,,, and

The following show side-by-side photos before and after for same or similar areas of our home. Note that the temperature difference between inside and outside is greater now than when the audit was conducted back in August (44° vs. 65°) as compared to (82° vs. 95°). A greater difference inside vs. outside would mean that any air movement would show up more easily in the FLIR camera.

Before photo of the porch
After photo of the porch.
We didn't make any changes to the porch, so the photos are essentially the same.

Before photo of the attic hatch.
After photo of the attic hatch.
The attic hatch shows a dramatic reduction in airflow. In the recent photo you can see the bolts and wing nuts, but you don't see any air leaking.

Bert's office before.
Bert's office after
I think this photo is pretty impressive also. In the earlier photo, you can see air moving between the ceiling joists. In the current photo you don't.

Basement sill before
Basement sill after
Here again, the movement of air was reduced. The difference in air flow for some of the areas is quite dramatic, but my overall airflow wasn't reduced by a whole lot as measured by the blower door. I was hoping for a really big reduction. I don't recall the exact number right now. Erik said this was to be expected to some extent. Our house was already pretty tight and it would take some more invasive work to drop it much lower. Nevertheless, we did control some important trouble areas-- like Bert's office and the work we did meets the minimum requirement for the rebate-- 25%*. That puts my ROI at between 6-7 years at current oil and electricity prices. 

* Erik said: "The final value for my home was 1585 CFM and the final savings [as calculated by the software] was 36%. I've mentioned a few times that EM's software is pretty generous but I'd be comfortable saying real world savings around 25% [that's the number I'm using]. Another question that may arise is whether the house is 'too tight' and that it 'needs to breathe'. The BTL (Building Tightness Limit; the engineered standard for necessary air flow) for your house was 1343 CFM50. That's the point at which you need to begin adding mechanical ventilation to make up for natural air flow. You can compensate with intermittent ventilation to 70% of BTL (940) after which dedicated continual ventilation is needed. So your house is well over the various air thresholds."

I can't wait to save money and be more comfortable this winter.



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