Buildings in San Francisco tend toward poor sealing because they can. When it’s never freezing outside, and rarely really hot (for now), there’s not a lot of functional cost to draftiness, lack of insulation, etc. This goes double for older buildings like our 1923 house. So I decided in 2019 to have a building efficiency expert come out and audit the house, hoping to reduce our gas usage as long as we still had our furnace, and to make it easier to use a heat pump instead in the future. After a bit of Google searching for energy auditors, I hired Alfredo from ELEM3NTS, who I can highly recommend— <clickbait>and you’ll never guess what he found!</clickbait>
Actually, what the auditor found should have been obvious in retrospect. Yes, we didn’t have as much insulation as we should. Yes, many of the windows were single-paned. No, that was not even close to the biggest problem with the house’s efficiency.
The biggest problem was the holes in the house. First among these was the fireplace: even with the flue nominally closed we were sending a good deal of hot air up the chimney, which in retrospect we should have been able to tell by the noise it made every cold, windy evening. Second were the old recessed light fixtures in the ceiling: incandescent bulbs enclosed in uninsulated metal boxes that conducted heat very efficiently out of the house, because the bulbs got too hot to safely insulate the enclosures. Third were a couple of windows and doors whose seals were just plain bad, enough that they might as well have been cracked open all the time. Fourth were some things I wouldn’t have ever thought of like electrical outlet enclosures.
The nice thing is that a bunch of these were cheaply remediable: cheaply both in money and in time. We never use the fireplace, so I covered the opening with a Fireplace Blocker blanket (the blanket fastens to the fireplace surround with magnets, but I found I had to augment that with double sided tape to get a good seal). I retrofitted the old recessed lights with Halo brand LED trims and caulked around the edges to create an airtight seal between the trim and the surrounding ceiling: you can do this with LEDs because they don’t get hot like halogens or incandescents. I put in new weatherstripping on the drafty windows and doors, which worked better in some cases than in others— our windows are weird old-style casements that don’t always seem to close properly over the weatherstripping, I still need to get an actual window expert in to look at some of them.
I’ve since found other sources that agree that air sealing is the first thing to work on for home efficiency and comfort, so I feel relatively comfortable making this a general recommendation. The ROI is hard to beat: even including the ~$1300 cost of the fancy efficiency audit, the sealing improvements cost thousands less than new attic insulation or replacement windows, and didn’t require any of the disruption to the house that cutting holes in the walls or ceiling to insert more insulation would have. We did eventually get underfloor insulation, because the house had none at all to start with, and the underfloor of the main level is readily accessible from the garage/crawlspace level so adding insulation there was non-disruptive.
All in all, we ended up with a house that subjectively feels much less drafty on foggy winter evenings. We didn’t really get a good chance to compare energy usage before and after, though, because soon after the audit we put in that heat pump… which will be the subject of the next post.