Thursday, August 3, 2017

Update and Things I Wish I'd Done Differently

A blog reader recently asked me to about the performance of the house now that it's a couple years post-occupancy so rather than answering him directly, I figured it's about time (OK, way past time) to post an update.

The short answer is that I'm very pleased with the performance of the house. I can walk around the place in jeans and a t-shirt on even the coldest winter day. There's never a draft, even when the winds come howling off the lake and hit the house straight on. And the snow lingers on my roof long after it's melted off every other roof in the neighborhood.

I'm using about 1000 kWh of electricity per month which might seem high for a energy efficient 1500 sq. ft. house, but around 250 kWh is used just to run the dehumidifier in the unfinished basement. Without that the humidity in the basement would quickly rise to levels where mildew would start to grow. It's a bit galling that so much of my energy budget goes toward this one function.

My other energy hog is a large saltwater aquarium system that consumes about 300 kWh of electricity per month. We all have our vices.

My heating calculations seemed to have been accurate enough as the small Fujitsu heat-pump I selected has been able to keep the house warm even on the coldest nights. The first winter I was in the house we had some long stretches of brutally cold weather with nights going down to -10 °F and days only going up to 0. During those nights the house would go down to about 60 °F - perfectly acceptable.

During the summer the heat-pump has more than enough power to keep the house cool, but I did make a mistake in not including a ducting system of some sort to bring the cool air up to the upstairs bedroom. This is not a problem in the winter as warm air naturally rises but in the summer it gets quite warm upstairs. I had hoped that the air-to-air heat exchange system would suffice for that but it doesn't come close.

Woulda', shoulda', coulda'


The main thing I would differently is that I wouldn't worry so much about energy efficiency! I got so caught up in energy efficiency that I completely dismissed the idea of a woodstove - a decision I now seriously regret. I'm trying to figure out how I might retrofit one in, but it's tough when you don't design it in in the first place. In the same vein, I wish I had more operable windows on the lake side of the house to let in the sounds of the outdoors during nice weather.

Construction-wise I would strongly consider cellulose-filled double-wall construction rather than covering the house with polyisocyanurate panels, primarily because of the cost. And stacking the roof with polyiso panels means lots of very long screws being driven through the roof sandwich searching for rafters, with the potential that many may miss their target. Plus it definitely complicates putting solar panels on a roof as most solar panel systems are designed to be bolted to the rafters.

I now wish I had gone with a cold roof system where there is an outside air gap between the roof itself and the insulated exterior of the building envelope. If there's a problem with a hot roof and water somehow gets into the insulation, it's difficult for the insulation to dry out. With a cold roof, any water that gets past the shingles winds up in the air gap where it can easily evaporate come dryer weather.

Another thing I would like to fix is the damper system on the exhaust hood for the stovetop. Sometimes when it's windy I can hear it opening and closing just from the wind. It's a straight open path for air to escape the house. Plus the hood itself is metal attached to a metal duct that extends to the outdoors so it's a pretty bad thermal short circuit. Because it does need to be fireproof the whole way there aren't a lot of solutions. 

Friday, January 23, 2015

Heat pump dryer

Whirlpool announced it back in July, I was able to order it in October and it wasn't delivered until yesterday (January 21), but I now own a real live, made for the U.S. market, heat pump clothes dryer. It's officially the Whirlpool HybridCare™ Duet Dryer with Heat Pump Technology.

Heat pump clothes dryers have been available for many years in Europe but this dryer and another recently announced from LG are the first to hit the U.S. market. I chose the Whirlpool over the LG primarily because the LG, for some reason, still has a vent to the outdoors. One of the major advantages of incorporating a heat pump into a clothes dryer is that the dryer can be ventless.  For a tight building enclosure that means one fewer penetration to be sealed. It also means that the dryer isn't taking conditioned air from the living space and venting it to the outdoors.

For those not familiar with heat-pump dryers, there's an explanation at the bottom of this post.

For now, here's the dryer:



Looks pretty much like every other clothes dryer, doesn't it? From this angle the only difference you can really see between a standard dryer and this dryer is the panel at the bottom right which opens to allow access to the secondary lint filter.

But look at the washing machine outlet box below. The two steel-braided hoses and the large black drain hose come from the washing machine. But that small copper tube attached to the small black hose is the drain from the dryer.



I ran a medium-large load tonight using the most efficient cycle and, well, it worked. It didn't seem to take terribly long (although I didn't time it) and the clothes came out not just dry but quite soft and with fewer wrinkles than the laundry from the last dryer I owned. In fact, the towels came out positively luxuriously soft. It is a bit louder than your typical dryer though - something to keep in mind if you're dryer isn't in an acoustically isolated area of your house.

The real downside to the dryer is the cost. I got it from ajmadison.com for $1399 with free shipping. That's a lot for a dryer. Of course, I'll save money every time I run a load, compared to a traditional dryer, right? To figure out how much I created this spreadsheet. It takes into account the amount of energy each dryer requires to run, the amount of energy a mini-split heating system would use to heat/cool the makeup air (for a venting dryer) and the fact that all of the energy used to run a heat-pump dryer stays in the house. This latter effect is a significant savings in the heating season and a significant cost in the cooling season.

According to these calculations, and based on prices for electricity and gas in Massachusetts, the costs per load are:
WinterSummer
traditional electric dryer:55¢53¢
traditional gas dryer:39¢38¢
heat pump electric dryer:17¢33¢

For a family that does 5 loads of drying a week, that's a savings of $1.90 per week during the winter and $1.00 per week during the summer for a heat-pump dryer vs. a traditional electric. Averaged out that comes to a savings of about $75 per year, which would bring the total lifetime cost of a heat pump dryer much closer to the cost of a traditional dryer. But unless you live in a very cold climate or dry an excessive amount of laundry, a heat-pump dryer, at today's prices, is unlikely to save you a lot of money.  If prices come down, or if the price of energy goes up, that could change.

While the cost may or may not be an issue, one great feature of this dryer that could turn it into a mainstream product is how much gentler it is on your clothes. Because it's not using heat alone to dry the clothes, it doesn't heat the air as much as a traditional dryer. Not only will clothes last longer but it might make it possible to dry clothes that you would otherwise need to hang dry.

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Here's the promised explanation of heat pump dryers:

A traditional dryer works by heating air, blowing it into the drum chamber, where it absorbs moisture from the clothes, and then exhausting the now moisture-laden hot air out of the dryer and out of the house. A condensing dryer, on the other hand, works by heating air, blowing it into the drum chamber and then pulling that warm moist air from the drum and cooling it to the point that the moisture condenses and drips into a collection tray. The cool dry air is then heated and recirculated back into the drum where it again picks up moisture and the cycle continues.

The tricky thing with a condensing dryer is how to cool the air being pulled from the drum.  Some condensing dryers use a metal plate that is air-cooled and some use a scheme that requires a steady supply of cold water. Neither of these systems results in a dryer that is any more energy-efficient than a traditional dryer and they are much slower. The market for condensing dryers has typically been apartment buildings where running an exhaust vent isn't feasible.

A heat-pump dryer is a kind of condensing dryer. Like pretty much every heat pump device, the heat pump in a heat pump dryer has a set of cold coils and a set of hot coils. This works out perfectly for a condensing dryer as the cold coils can be used to cool the warm moist air coming from the drum and the hot coils can be used to heat the air before sending it back. Heat pump dryers use 40% to 50% as much electricity as a traditional electric dryer and dry clothes much faster than condensing dryers that don't use heat pumps, but still slower than a traditional dryer.

Saturday, November 22, 2014

Moved in

Well, I still have a dumpster in my driveway, no kick-plates on my kitchen cabinets, lots of unfinished trim, no screens on the screen porch and a zillion other little things but the house is done enough that I was finally able to get my occupancy permit and move in!


 In the pic above you can see the outdoor part of the mini-split heat pump.


 On the right in the photo above you can see the intake and exhaust for the HRV.


You can spend a fortune on lighting fixtures.  These pendants about the island were $14.99 from IKEA.


The wall-to-wall carpet in the bedroom is Mohawk Everstrand, a product made from recycled plastic bottles.  It's not the absolute softest carpeting one can buy but it's pretty darn soft.   Mohawk claims they recycle 14,000 plastic bottles every minute making this carpeting!



Installed the kitchen myself - which is why the kick-plates have yet to be installed.  Total cost of the kitchen was about $7000 not including my labor. $4000 more for appliances. If you've ever built a kitchen you'll know how inexpensive that is.  I can't say enough about IKEA cabinets.  Solid, well engineered and remarkably inexpensive.  Of course, you have to install them yourself.  Pretty easy to do until you get to the island where some intermediate carpentry skills come in handy.

The refrigerator is this one from Summit Appliance.  It's not huge but it's counter depth, very well laid out and very quiet.

The range is from Sears.  It's an electric induction range which so far seems to be working great.  I do have to buy new pots and pans as my old stuff was aluminum which doesn't work with induction.



In the picture above you can see where fresh air comes into the house just above the heat pump unit. The idea here is that the cool fresh air will mix with the warm air from the heat pump unit preventing a cool draft from the fresh air vent.  So far it seems to be working well.

The heat pump is the smallest available from Fujitsu that has managed to keep the house comfortable on some 25° F nights we've had recently, even though I'm running the HRV on high.  I plan on running the HRV on high for the first year or so to keep the indoor air quality high during the period of highest out-gassing of any of the finish materials or new furniture.

And that big empty spot below the heat pump - that's where the aquarium is going to go!

I will continue to post on this blog to report on how the house is performing as well as to fill in some details that I never got around to discussing, so keep checking back.


Monday, June 30, 2014

Landscaping

There's still plenty to do in the interior but April and May are the best months for putting in a new lawn and planting shrubs.  The whole yard is just dirt at this point from all the trucks and machines rolling over it these past few months. While in some ways, I hate to plant a big lawn that'll need to be mowed every week, it's important to stabilize the soil so that the rain doesn't erode it all away into the lake.  In fact, the building inspector won't issue a certificate of occupancy until the site is stabilized against erosion.

My landscaping plan calls for reducing the grade of the back yard by building a retaining wall several feet back from the lake.  This should give me a more usable back yard, slow down the rain runoff as it moves toward the lake, and create a border between the wild growth by the lake's edge and the lawn area.

I hired Ed Coykendall and his company Landscape Artisans, to do the work.


The retaining wall under construction



This is the section of the wall where we'll attach the wooden steps that lead down to the dock.


Done

A few months laters with the stairs down to the lake.

The sidewalk going in in the front





Graded, shrubbed and seeded


Hmmm, what's that?

Ah, someone else likes my new yard

Looks like at some point this summer I'm going to be seeing some baby
turtles coming up out of the lawn.


Looks like a house!


Wednesday, April 30, 2014

Cavity insulation and finish work

To complete the insulation, we first sprayed a layer of closed cell foam on the basement ceiling. Closed cell is quite a bit more expensive than open cell but the basement is outside the thermal envelope of the house and the closed cell foam will provide the air barrier.  We hired a company called Green Cocoon to do the work.


The closed cell foam has a slight greenish tint to it.  I only had a single layer (about 2") applied to save on cost.




After installing the foam, we added batts of Roxul mineral wool for a big boost to the R-value at a relatively low cost.  The Roxul also provides fire resistance, which otherwise would have had to be provided by spraying a fire resistant coating onto the closed cell foam.  The coating actually costs way more than the Roxul but provides no additional insulation.


Upstairs we sprayed in open-cell foam since we weren't depending on the foam as an air barrier.



In the picture below you can see that they do every other cavity, to make it easier to trim the overflow.






Prestained knotty pine arrives from Duragroove.  Two palettes remain in the picture below but there was a third one when we started.  The boards are all 16 feet long and since I couldn't find my extended fork lift we had to unload it all by hand.



And here's what it looks like installed.



In the picture below you can see the indoor unit for the heating/AC system.  That one unit is supposed to be able to heat the entire house.  Above it you can see the vent from which fresh air will come into the house. Since that air will be colder (in the winter) than the air in the house, putting the vent above the heating unit will hopefully temper any cool breeze from the fresh air vent.