Following on from yesterday's post, just for fun I adjusted my model to the original Victorian condition of the house by removing all insulation and the vinyl siding from the model. I then guesstimated that without the exterior storm windows, no weatherstripping, and no vinyl siding (so air could sneak in between the clapboards), the blower door would have pulled 8000cfm.
I then contrasted that in the graph above with my estimate of the present energy losses of the house (expressed in millions of BTU per heating season), and with the condition after my estimates of Snug Planet's proposed project. I now have an estimated blower door target from them of 2500cfm so I put that in rather than yesterday's 1800cfm. Finally, in response to yesterday's post, several commenters suggested adding tight-fitting seasonal interior storm windows to the existing windows. Assuming that raises the window R value to 3 and cuts the remaining infiltration to 1200cfm @50Pa, that gives me the fourth stack in the graph.
Several conclusions come from this:
- Previous owners were rational in the things they did - they tackled the lowest hanging fruit and the house is much more efficient as a result.
- What Snug Planet wants to do is also rational and would be a large and clear improvement and probably does represent the next set of lowest hanging fruit.
- However, it seems like adding some kind of interior storm windows is intriguing and I want to explore the feasibility and cost-effectiveness of that.