Tuesday, April 28, 2009

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.

Friday, April 24, 2009

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.]

Monday, April 20, 2009

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.

Sunday, April 19, 2009

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.

Saturday, April 18, 2009

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.

Friday, April 17, 2009

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.

Thursday, April 9, 2009

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.

Tax Credits for Homeowners: Energy Upgrades


I found a wonderful summary of federal tax incentives available to homeowners that choose to make energy efficiency upgrades. This is courtesy of the U.S. EPA's Energy Star program.

Tuesday, April 7, 2009

Home Energy Audits: The Infrared Advantage

It's fair to say that this house has more than its share of air leaks. The real challenge is to prioritize. That's where the infrared imagery from the energy audit comes in handy. Big leaks come before the little ones. Infrared (IR) imagery helps to put an order of magnitude on these opportunities.
In this case, we're looking at the floor in the dining room where a bay window bump-out extends from the north face of the house. This is an overhang; you can actually go outside and stand beneath this area:

One task for me is to remove the shoe molding and fill behind with caulk or expandable "foam in a can." The other task is to remove the external planking beneath this and install insulation. Given the space available, that insulation will probably be one-inch thick rigid board.

Friday, April 3, 2009

Energy Audits: Revealing Your Home's "Second Price Tag"

The province of Ontario is currently considering a bill that makes energy audits a legal prerequisite to the sale of a home. As you might suspect, this is generating some spirited debate. But the argument brings light to a little recognized fact: a house has two price tags. Here's what I mean:

1. There's the price indicated in the traditional settlement transaction that passes the property title from one owner to the next.

2. There's the present value of all inputs that the house will require for proper upkeep. This covers everything from repairs and maintenance to-- you guessed it-- utility consumption. The new owner will be obligated to make these outlays for as long as he or she owns the property.

The idea here is that a proper energy audit is a window on a property's future energy liabilities. Ideally, the report should show how the house's energy consumption compares to structures of similar size, configuration, appliance profile, etc. Such a comparison requires an analysis of the utility bill history for the property; an inventory and diagnosis of heating, ventilation, and air conditioning systems; and an evaluation of leaks in the building shell.

You can't predict future energy prices. But you can use a recent annual utility bill history for comparison to average home data. This is a reasonable way to get a relative measure of the "second price tag" that prospective buyers should consider when purchasing a home.

Thursday, April 2, 2009

Energy Star Home Energy Yardstick

There are a LOT of Internet-based, do-it-yourself tools for calculating home energy use. The grand-daddy of these sites is The U.S. Environmental Agency's Energy Star platform.

The "Home Energy Yardstick" is typical of free, online resources. This tool allows you to compare your home's energy consumption to national averages. So, since I already maintain a spreadsheet with my historical utility bill data, it was a fairly simple task to enter a handful of numbers like the house's square footage, zip code, annual consumption and expenditure figures for gas and electricity, and so on.

With the press of the "enter" button, my results emerge: a humbling 5.9 on a scale of 1 to 10, where 10 is "most efficient." The screen also provides a list of prescribed improvements, with links to explanatory pages elsewhere in the Energy Star archive.

Note that national averages are based on other homeowners' self-reported data, which may or may not be correctly entered. However wobbly the data, it's better than nothing. By investigating this alternative route, I find the same leading recommendation: seal the air leaks and improve insulation. The only way to improve this tool is to provide an estimation of dollar savings-- but that result is obviously dependent on the specific improvements that the homeowner elects to make. To be fair, the model can't measure what has yet to be done.

The Blower Door Test

The critical part of our home energy audit was the blower door test. In so many words, this is a diagnostic that measures how much the house leaks. "Leakiness" is crucial for quantifying energy waste. This is not a question of eliminating air infiltration, but instead optimizing it. The house needs to breathe, especially so that excess water vapor can escape. If it doesn't, you develop mold problems. At the other extreme, if too much air escapes, your furnace and air conditioner have to run longer to compensate-- driving up your utility bill in the process.

The blower door test puts a physical measure on air flow in and out of the house. To conduct this test, the audit technician sets up an apparatus like the one shown in the picture:

The key component is a high-power electric fan that essentially sucks air out of the house. To conduct this test, all other doors and windows are closed, and all house fans plus the clothes dryer are turned on. The remaining gaps and penetrations are then the collective "pathway" for air infiltration. Gauges on the blower door apparatus indicate the volume of air movement, measured in cubic feet per minute (CFM). The data generated by these gauges are compared to engineering standards for how much air should infiltrate a house of a given square footage.

The results for us: A house of our size should be "breathing" at a rate of 1,800 CFM. The blower door test shows that the current rate is like 5,300 CFM-- three times what it should be. Before this test, I had only a vague understanding of my home's heat loss. My understanding now has an order of magnitude-- which is my motivation to do something about it.

Only one word of caution: the blower door test moves a SERIOUS volume of air. Nothing in the house was disturbed or damaged. But I will say that it effectively pulls dust out of every imaginable recess, like from the interior spaces between walls. Don't be surprised if the house has develops a musty odor for this reason. Fortunately, it dissipates after half a day or so.

The number-one item on my summer improvement list is to seal air leaks. We'll discuss that exercise in future posts.

Wednesday, April 1, 2009

The Drafty Door Issue

A few years ago, we remodeled the kitchen. I decided at the time to replace the old kitchen door that provides access to the back yard. I thought I was being frugal in merely replacing the slab (i.e. the "door" panel itself) while leaving behind the jamb and related trim.

Bad choice. I got the new slab to fit, but it was a chore and the results weren't great. Subsequent weather stripping was only a partial solution. Consequence: we experienced some ferocious drafts around the door, especially on the coldest of winter days. LESSON LEARNED: install pre-hung doors! They are manufactured to provide a snug, weather-sealed fit.

Our energy audit confirmed what I already new to be true: this calls for a retrofit. This will be a do-it-yourself job for later this summer when the weather gets warmer. I expect to pay about $250 for materials.

"Free" Home Energy Audits

I'm not sure why, exactly, but a lot of people expect energy audits to be gratis, free of charge. Lo and behold, there are a couple forms of "free" energy audits available to homeowners: those provided by utility companies, and those provided by vendors of certain home improvement products. If you were to investigate, here's what you'd find out:

Utility-provided energy audits.
This service is often provided in response to consumer complaints about rising energy bills. It's a good idea, but think about it: how many resources can a company put into a service that generates no revenue? Despite the best of intentions, a "free" energy audit purposely cuts corners to produce what is often a simple, generic checklist. Not much in the way of cost-benefit analysis specific to YOUR situation.

Vendor-supplied energy audits.
Let's put is this way: If you get an energy audit from a company that installs windows, don't be surprised if their report concludes that your best option for saving money is to buy new windows.

That leaves you with the option of actually paying for an energy audit. This means making an outlay for the time and expertise that it takes to thoroughly diagnose your home's building envelope and appliance functionality. It means paying for a report that provides a cost-benefit analysis of specific improvements for your home.