Friday, March 15, 2013

Initial Report on Our Household Energy Project


Last March, I reported on the results of an energy audit that we had done on our circa 1850 farmhouse in the hills of upstate New York, together with expected results of the project the contractor proposed to perform to improve our efficiency (1, 2, 3, and 4).  It took a while to get the project organized and approved, but eventually it went ahead in September of last year.

Today I wanted to give an initial report on how things are working out so far.  It would have been ideal to wait until the end of the heating season, but it happens that we were asked to be on the Dryden Resource Awareness Coalition's energy tour tomorrow morning (Saturday), and so I'm doing some calculations now to be able to give information to tour participants.  (Any readers in the area are welcome to drop by - time and place information at the link above).

To recap, when we first moved in, we had a wood stove and pre-existing baseboard electric heat.  The wood stove could not keep the entire house to a reasonable temperature, and the baseboard heat was used extensively.  We had an energy audit performed and it turned up a variety of issues.  Although the walls were insulated tolerably well, and the attic was insulated, a lot else was not great.  In particular, the house was balloon framed and a lot of the interior walls opened into the attic.  The stone basement was vented to the outside, and was extremely damp - water dripping from the floor joists and plumbing year round, frequently standing water on the basement floor.  Overall, the house allowed a very high level of infiltration - 5155 cubic feet per minute at 50 pascals pressure difference.  It's likely that in practice a lot of infiltration took the form of cold air we being pulled into the basement, up through the flooring into the house and then out the attic, due to the stack effect.

Snug Planet proposed to do work in four main areas.  They air sealed all the gaps in the attic and blew in additional cellulose insulation to bring it up to R-49.  They air and moisture sealed the basement using a mixture of heavy plastic fabric and spray foam.  They reinsulated a small side-attic in our house that had a lot of very poorly installed ragged fiberglass.  And they replaced a number of our older appliances with high-efficiency modern ones; most significantly, a new heat-pump hot water heater.  All of this was done via New York State's on-bill recovery financing over 15 years - we put out essentially no cash for all the work.

Here's a few photos to illustrate the work.  Here's the side attic, with the ragged fiberglass replaced with a neat box of foil-faced polyisocyanurate which encloses the plumbing in the wall to the right (there's a bathroom on the other side of this):


Here's the basement, no longer a muddy stone-walled hole in the ground:


The ragged fiberglass between the floor joists was pre-existing.  You can imagine how well that was working.

We added the carpet to protect the plastic membrane and drain matting on the floor.  The vertical strips of carpet lead to crawl spaces off the main basement.  They are there so the cat can easily patrol the whole area for mice without scratching the plastic (you can see the cat bowls in the right foreground).

The project has made the basement usable for certain applications which don't fit well elsewhere in the house:


Previously, it was pretty unusable space because it was so damp and unpleasant.  Here's a detail of spray foam sealing of the stonework:


Flopsy the cat is in there too, if you look carefully in the shadows, as she was very intrigued by my intrusion into her domain.

Here's the heat pump hot-water heater:


So far, this has been performing its appointed function with no fuss or difficulty of any kind.  It is noisier than an immersion-type heater, but we don't notice the noise down in the basement.  It uses less than half as much electricity as the most efficient immersion heaters.

Between all the air sealing and the hot water heater (which extracts water from the air and sends it via a plastic line to the sump pump at the lowest point in the basement), the basement conditions are now much healthier:


I didn't measure the humidity before the project, but with water dripping off all the plumbing, I assume it was pretty much 100% all the time.  I have a dehumidifier down there, but it's turned off at present.  We may need it in the summer.

So how did all this do at actually saving energy?  The most immediately striking effect was on the icicles hanging off the roof in January - we didn't have any, whereas most of our neighbors had a lot, some up to six feet long.  This indicates that we have far less heat leaking into the attic than we used to.

Because wood is much cheaper than electricity, we elected to continue to use the wood stove continually throughout the winter, much as we had the previous winter.  In both cases, we got through about 3 1/2 cords of wood, so there was no saving there.  However, the electricity saving was dramatic:


The darker blue line shows cumulative electricity usage through the winter of 2011-2012.  The red line shows this last winter, to date.  This winter was colder than last winter, so the pale blue line shows my estimate of what the electricity usage would have been last winter if it was as cold as this winter (ie corrected for the greater number of HDD - heating degree days).  You can see that overall we cut our electric usage by about two thirds.

It's worth acknowledging a couple of limitations here.  Firstly, heating almost exclusively with wood means a living room (where the stove is) that generally runs about 75-80oF during the day.  Then the outlying areas of the house might get up to 65oF in the afternoon, and fall to 60oF at night.  So this is not American standard 72oF everywhere.  We kind of like it this way - a very warm cozy living room, and then cooler in the bedrooms, but not everyone might.  Also, my wife is a full-time homemaker, and I was telecommuting to my job for most of this period.  We are around a lot to keep the stove fed.  A dual career family would probably need a pellet stove to accomplish a similar result.  Also, a couple of rooms at the opposite end of the house from the stove would never stay warm enough and we used the electric baseboard sparingly to keep them usable.

While we are saving a lot of electricity, are we saving money?  Here we have to account for the fact that we have now added a $123/month payment to our electricity bill for the work that was done.  This next graph compares the cumulative cost of utility bills this winter (red, including the loan payment), to last winter (blue, including the correction for temperature):


You can see that we saved almost $1000 through the heating season.  It's not clear yet whether we will save money in the summer when we only have the benefit of the more efficient appliances to offset the loan payment.  However, we have almost certainly saved enough in the winter to offset any possible loss in the summer.

Finally,  I want to report on how reality so far compared to my projections based on a heat flow model of the house.  This last graph shows as the left two columns my estimate of heat inputs and outflows from the house done last spring.  The right columns show my estimates now:


My projection of electricity usage was accurate to within 3% (which must be a fluke to a significant degree).  However, we used an additional cord of wood relative to what I expected.  The main reason is likely that the project did not cut infiltration as much as I had hoped.  I was projecting a final blower door measurement of 2500cfm@50pa, but Snug Planet actually achieved 3300cfm@50pa (vs the original 5155cfm@50pa).

Overall, while the project didn't cut energy usage quite as much as I projected, the project economics are still very clearly positive.  Furthermore, we created a large new storage/utility space in the basement, which was previously unusable, and probably extended the life of the ground floor joists significantly.  We also got a number of new appliances.  All for zero cash outlay.  I'm pretty happy so far.

16 comments:

Aaron said...

Very cool.

I don't know what kind of woodstove you have but if you don't have a Woodstock catalytic stove you could save about 25% - I don't know exactly but 20 to 25% less burnt wood seems to be about the right amount of savings. (I've read forum posts that others see about the same savings).

Most catalytic stoves have a bad reputation but Woodstock seems to have got it right. It's hard to find a negative comment. They're expensive stoves but I consider it worth every penny. The concept it simple - the catalytic combustor allows the wood to burn at lower temperatures which utilizes more of the woodgas - a virtually smokeless stack.

It takes a bit more thought and care - you have to bring it up to temp and then kick in the combustor. It also requires very well seasoned wood. But they're beautiful stoves and a joy to work with.

I've never heard of a heat pump hot-water heater - thanks for the tip!

bmerson said...

That loan program seems like a great program. It would be great if the US would institute a green bank for such programs at the federal level, making them available to all American households.

Congratulations on the results so far.

Stuart Staniford said...

Aaron - we have a Lopi Endeavor, which we love. It's supposed to be about 75% efficient. It relies on secondary burning (via overhead air injection tubes) rather than catalytic converter. Seems to work pretty well.

Greg T. Jeffers said...

Excellent; and inspiring as well.

Greg T. Jeffers said...

I love micro solutions to practical problems/personal finance issues likr this.

Daniel Ridgeway said...

It is kind of hard to decrease infiltration when you are sending your conditioned air up the chimney. The replacement air has to come from somewhere. A woodsove that is sealed and has a make-up air kit would be better.

Stephen B. said...

You did well on the basement.

I'm trying to do similarly, though since my basement walls are newer (1950s), they're straight poured concrete. So far I've poured a new concrete floor with vapor barrier and have sealed the walls with sodium silicate. Next comes the part I'm looking forward to - rigid foam on the walls, probably 2 layers of 2" panels, along with spray foam on the inside of the sill areas at the top.

A sealed, insulated basement transforms a house that was suffering from a drafty, damp basement previously.

My electric utility is giving substantial rebates on mini-split heat pumps as well, so I may install one to back up the wood heat (also to be installed.)

oji said...

Thanks for this post. Very interesting and practical.

A little surprised you stopped at R-49. with roughly the same climate as yours, last fall we went from R-30 to R-60, and it's reduced heating energy use by a solid 20% (natgas). With a tax credit as well, it's been well worth it-- and wait until the fracking bust!

Greg said...

Thanks for the update, Stuart.

That's very impressive, especially considering the age of the house.

Old houses are always going to have infiltration problems - old building techniques were designed to keep air circulating, because builders were well aware of the problems damp can cause. So you did well cutting down the infiltration as much as you have.

Stuart Staniford said...

Daniel:

An outside intake for the woodstove is on my list of projects to do. However, I doubt it would have contributed much to the blower door number as it was out and fully damped down at the time of the test. I imagine most of our remaining infiltration is some mix of Victorian windows, and an old house with no housewrap allowing a lot of air through the walls.

Stuart Staniford said...

oji: if you look carefully at the "Actual Outflow" column in the last graph you can see the very small bar for "Attic". At this point, further insulation in the attic would do me very litte good as I have much larger heat losses elsewhere.

Aaron said...

"Aaron - we have a Lopi Endeavor, which we love. It's supposed to be about 75% efficient. It relies on secondary burning (via overhead air injection tubes) rather than catalytic converter. Seems to work pretty well."

That's funny - we recently moved from off-grid back onto the grid and our new house came with a woodstove - a Lopi (I think it's an Endeavor) that has the overhead secondary burn tubes. I've been lazy and haven't switched it out with our Woodstock Fireview so I've been using it all winter. I find getting the secondary burn going to be more challenging than with the Woodstock Fireview. The Lopi is a good stove but IMO not as good (or as efficient) as a Woodstock.

kjmclark said...

To agree and disagree with Aaron, I bet he's right about the Woodstock, but having a Lopi (Parlor), I wouldn't want to switch. We use that lower-level surface for cooking/heating a *lot*. It's busy boiling down our backyard maple-tree's sap right now.

On burn efficiency, I suspect we manage better than 75% with ours. The trick is to think of smoke as wasted fuel, and avoid conditions that produce smoke. That means seasoning the wood yourself (instead of trusting someone else to have done it), getting the stove up to 400F+ quickly, and maintaining it hot. The secondary combustion works really well with a hot stove. We bought a magnetic thermometer that we put on the side wall of our stove, and keep it in a range of 400-600 on that thermometer.

And a ceiling fan works wonders for heat distribution.

Mike Aucott said...

We get about half of our heat from wood, and I concur on two things that have been said; the importance of a direct feed of outside air to the stove only and the importance of burning well-seasoned wood.

Clearly, if the stove is pulling heated air from inside the house for combustion, you are losing heat and driving infiltration of cold air into the house. Also, well-seasoned wood burns better and produces more heat since there's less water being driven off. To be well-seasoned, wood must be cut and split over a year prior to when you burn it. What the firewood guys sell is usually not truly well-seasoned in my experience.

Mike Aucott said...

And congragulations Stuart, huge gains!

Ted Kidd said...

Nicely tracked and documented!!