Degrees of Heat and Consumption

Let no one, least of all me, be surprised by the relationship between average monthly temperature and a domestic household's monthly therm (natural gas) consumption. Thanks to archived utility bill data, I can plot the January-December gas consumption onward from January 2005:


Two things jump out at me in this picture. First, before 2006, I was not in the habit of turning off the power supply to the boiler each May 1. It ran on standby all summer long. Hence, with the boiler running in 2005, my total natural gas consumption during the summer months was effectively DOUBLE what it should have been for that period. The second point is the normal summer months give me an idea of how much gas is devoted to water heating and cooking combined, since those are the only other gas appliances in use.

The take-away here is that the year-on-year data trends are a way of detecting anomalies in consumption. Note however that this is not "real time" error detection; in effect, such information becomes evident when you get your utility bill, usually a couple weeks after the meter reading date. It's better than nothing, but certainly not as useful as having sub-meters for each appliance. And while electricity submetering is fairly easy to do for domestic appliances, even I am not inclined to pursue that... not yet, at least.

Air Infiltration Around the Dryer Vent

Now I need to decide what to do around the dryer vent. Our dryer is immediately off the kitchen. It's right next to an exterior wall, so the vent has a very short run. However, this configuration allows a LOT of air leakage:


One option is to seal around the orifice with the appropriate insulating material. But what? The foam-in-a-can stuff is combustible above 240 degrees fahrenheit; I'm reading that the high setting on a clothes dryer approaches 350 degrees. Another option involves this contraption:

I know very little about it, other than its supporting webpage.

The blogger at Dover Projects provided a thoughtful post on the same subject. A similar discussion is on Green Talk.

[Post script: I eventually installed one of these; the story is here.]

Insulation DOES Make a Difference

Back to work this morning in the home office. This is located directly beneath the attic area where I was crawling around last Saturday, air-sealing and carefully cutting insulation batts to fit.

The path of heat flow is much like water. If you want to stop a river's flow, a few big obstacles in the river bed just won't do the job-- you need to build a dam. Similarly, you can't insulate an attic without carefully covering the entire surface-- ensuring a snug fit between the ceiling joists, all the way out to the top sills of the walls.

Given the current outside temperature of 46 degrees, the boiler is operating, and the radiators are doing their job. This room is now noticeably warmer than it was before. Lesson learned: partial insulation has the same effect as no insulation. Dare I say it, last Saturday's adventure was worthwhile.

The Day After Day One

I've earned my day of rest, so for today's post, I thought I'd share some unexpected highlights from yesterday's experience, good and bad.

First the bad: Performing air-sealing tasks in the attic space over the rear addition got me in direct contact with some vile grit that stained my hands (shame on me for not wearing gloves). This stuff just won't come off:


Now, a bit of background: At some point (probably in the 1970s), a previous owner of this house had stuffed the rim joists with unbacked fiberglass insulation. This measure was of limited effectiveness; I could tell because this insulation was soot-stained by air infiltration. There had been no effort to seal the gaps between the wood frame and the masonry. So I have been pulling out this insulation with the intention of bagging it in small plastic bags for re-stuffing into tight spots where I can't effectively reach (like the corners of the attic). In removing this stuff, I discovered some artifacts that had been tucked away in the space under the floor of the bay-window bump-out. This is a sturdy cardboard box, about six inches square and two inches deep. The label reads "Hochschild Kohn, Hardwater Soap, Baltimore." The box was empty, except perhaps for some mold spores.


A tad more fascinating, to me at least, was this object:


I believe this is cap from a streetcar motorman's uniform. We have the deed history to this house, so I know the name of the first owners, who were here from 1915 until about 1957. Using online U.S. census data from 1930 and before, I could track down more info about them, like occupation. Sure enough, the original man-of-the-house was listed in the 1910 census as a "streetcar motorman." During the ensuing decade, he exchanged that job for one with the phone company, got married, and took up residence in this house which was built in 1915. All of this could be gleaned from a review of the 1920 census. The motorman's cap was valuable enough to be tucked away in the basement, but not so valuable that it was remembered. Like the soap box, the cap was lost to oblivion until discovered in 2009 by an energy geek homeowner.

Home Energy Audit: Getting Down to Work

At some point, I actually have to do some work to realize the benefits of a home energy audit.

Well, today was the day to get started. I chose what would be one of the hardest spaces to address: above the ceiling of the rear addition. This space has an extremely shallow roof that gives no more than 30 inches clearance at its highest point. This is some TIGHT space. The the overhead is so low that I couldn't even crawl on my hands and knees. I had to slither around like a snake. The footprint of this area is about 8' by 20'.

Last year, and this was before I got the energy audit, I cut away a portion of the inner roof to make hatch to provide access to this space:


At the time, the intent was to insulate the area with R-30 batts of fiberglass wool with kraft paper backing. Having since read up on air sealing, I later realized that I hadn't done a very good job of fitting the batts in the outer, most shallow areas. This is how NOT to fit fiberglass batts:


The infrared images from my energy audit, taken from the floor below, showed where heat was radiating through the ceiling thanks to the gaps I left. So today, I opened up the hatch to this area and began several tasks:

1. Sealing the top of the exterior walls (foam in a can)
2. Fitting styrofoam baffles to the underside of the roof sheathing, which allows air to move from the soffits, and
3. Cutting insulation batts to FIT this time in those tight corner areas.

I'm satisfied with the results this time.


Let me tell you: this work demanded some physical contortion. I wore a respirator, but no gloves. I got stuff on my hands that so far has resisted soap, alcohol, and turpentine. It was time-consuming and down-right exhausting. While I was doing this, I imagined paying someone to do this work. You have to ask yourself-- how well would the job be done? I'm sure that vendors run the gamut from great to gawd-awful, but you can easily imagine someone taking short-cuts to get out of a space like this as quickly as possible. So, yup, I did it myself, and it took about four hours including a couple breaks. Just me, a portable light fixture, a utility knife, a staple gun, a couple cans of foam, and a steadily rising temperature. I was glad when this was over with. But I KNOW that it's done.

Air Infiltration Around Floor Rim Joists

One task that awaits me is inspection of the interface between the masonry foundation and the wood frame structure above it. The floor joists essentially sit on the masonry, capped by the rim joist which runs parallel to the foundation wall and perpendicular to the joists. A house does not have to be 94 years old to yield voids in this interface between stone and wood. Gaps promote not only air infiltration, but also provide entry for spiders and the like. At some of the corners, mice might even be able to whittle a pathway or two.

Here's a view from beneath the deck.
This is actually outside. You're looking at the wall to the crawl space under the kitchen. The joist-to-foundation interface is pretty obvious. I will work on this with a combination of caulk and foam-in-a-can stuff. I know I mention that a lot. I'll need plenty, I think.

About Attics, Air Leaks, and Foam-in-a-Can...

This photo was taken in the attic, behind the knee wall:


The masonry to the rear is a chimney. The seam where the chimney meets the framing has some gap-filling foam applied (the pale yellow stuff in the upper right corner), but it's poorly done and clearly not finished yet. The slats in the foreground are plaster lath for the ceiling below. The one-by-six plank to the left of the image is an attic floor joist. In the center of this image, parallel to the joist and running perpendicular to the lath strips, is wall top plate (that is, the top of a wall which is located in the room immediately below). All the literature points to wall top plates as a source of air leakage from conditioned space (below) into the attic. The medicine here is to seal the top plate with expandable foam. The foam, when still wet, is also a great adhesive; one can "glue" down a plank wide enough to form an air-tight cap over the top plate. A similar cap needs to be placed over the exterior wall top plate, which can be seen here running from left to right in the back of the image, immediately in front of the masonry.