More Musings of an Energy Nerd
A friend of mine is planning to build a house, and he recently sent me an email with a question: “I can’t help but wonder, ‘What would Martin build?’ ”
I’m still living in the house I built in the 1970s, so my first reaction was, “Whatever you do, don’t build a house like the one I built.” My leaky house has never been tested with a blower door—and that’s probably a good thing, because the building’s air leakage rate must be embarrassingly high.
I answered my friend’s email as best I could. But there’s a lot to say on the topic—so I decided to jot down my ideas in the form of this article.
Longtime readers of GBA will recognize much of the advice I’m about to present. While these opinions may not all be fresh, some readers may appreciate having all these threads pulled together in one place.
Have you ever built a house?
A few readers have already had the pleasure of designing and building a house. If you’re one of those, you probably know how privileged you are. Designing and building your own house is expensive. If you did it 40 years ago, as I did, you probably realize that the task has only gotten harder recently.
In the U.S., our housing affordability crisis is worsening. Rents are high and rising. In most communities, it’s increasingly difficult to buy a building lot. Building code enforcement is stricter than it used to be. Permitting costs, as well as the costs of connecting to utilities, are way up. And supply bottlenecks associated with the pandemic have caused huge increases in building materials costs.
If you can still swing the numbers for a new construction project, be grateful—and…
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37 Comments
" and you don't want in floor hydronic heating." Whats the story behind this statement? why not?
I think the argument here is that in a tight, well-insulated house, the heating load is so low that in-floor hydronic heat would provide sufficient comfort at a floor temperature barely above room temperature -- running it at the "toasty warm floors" level that people imagine would way overheat the space. Also, in a tight, well-insulated house, floors without heat will be nominally room temperature, not cold from inadequate insulation below, and with good quality windows and exterior wall insulation, the mean radiant temperature effects are mostly negated. With those benefits gone, in-floor heat is left as a quite expensive and difficult to repair option, with no real benefits over other lower-cost and easier to maintain heating systems.
With a highly insulated, and airtight house, there's very little heat load required. Your in floor heat will hardly ever be on, so you probably won't get the warm floor goodness.
If you figure the cost of the in floor heating vs one or two mini splits, it will probably be significant.
Then there's the energy cost of heating the water, vs an air source heat pump.
Carmenooch,
To learn why you don't want in-floor hydronic heating, read this article: "All About Radiant Floors."
Martin,
I took a look at the article you linked to. Referencing the below can you explain what the advantages (or what Alex Wilson would say the advantages are) would be for in-floor radiant heating in an old house?
Many authors have quoted Alex Wilson’s conclusion that a radiant floor heating system is “a great heating system for lousy houses.”
Thanks for the assistance.
Andrew
Andrew,
If you live in a poorly insulated, leaky house, your feet may always feel cold in the winter. I suppose you could spend $15,000 or $20,000 to install in-floor hydronic heat to solve the problem -- but it would make a lot more sense to spend the same amount of money on air sealing and insulation.
Thank you for this perspective Martin. The pretty good house guys have some similar advice. I think I saw that Dan Kolbert et al have a book due out next year.
https://www.prettygoodhouse.org/
It’s true that affordability is quite a dilemma, even for an owner-builder with a plan for a mall house.
In my case an undeveloped village lot cost $115k. Site work and utilities might add $40k. According to the builder I work for, our materials/labor ratio on custom homes is somewhere between 60/40 and 70/30. I am anticipating approximately 3500 hours labor on approximately 1200 square feet. That’s at least 5 years hard labor nights and weekends. I am not far enough along to cost out materials, but I’m hoping if we keep things simple and use as much local and natural material as possible, that we can come in under $200k.
The tiny 2 bedroom house for sale next store suddenly doesn’t look so crazy at $240,000.
Thanks Martin for all your advice. I'm just finishing up building my own house that I started two years ago and reading your book and articles on GBA definitely has a big influence on the design. It's great to have it all summarized here in one place.
House details:
-2200 sqft 4 bedrooms with 600 sqft mother-in-law apartment above the garage
- 2x6 walls with cellulose zip system and 4in exterior mineral wool insulation, rainscreen and T&G cedar siding
- Triple glazed tilt-turn windows.
- All electric with ductless mini splits, HP water heater, induction cooktop and 8kw of solar
- .6 ACH50 blower door test with Zehnder ERV for ventilation.
I did the majority of the work myself and bought a lot of my materials before prices increased. Currently we are on track to be all in including land and site work at $420,000.
Unfortunately spending two years building your own house with a good flexible daytime job to support it isn't a scalable solution to affordable housing. For those that can build their own house it really is a privilege and a rewarding experience.
absolutely fantastic looking home.
Fantastic plus. It would be great if you could post more details about your build.
I agree. More details please!
Great read, Martin. Given that you are recommending a vented, unconditioned attic, what's your recommendation for air-sealing the junction between the house and the attic (ie ceiling and/or attic floor)? Where does the electric run? Does it run in among the insulation? Hmmm, ok I followed the link you had (love your linking) so basically a pre-insulation, post-electrical, air-seal of the drywall level from above.
I think the approach described in the most recent fine homebuilding magazine would be a great complement to your approach. They add joists as though for a second floor then zip sheathing forming a hard, horizontal lid taped on top of that before adding the trusses. The joists then form a deep service cavity for electric, lights (including the dreaded can lights!) and ducts. https://www.finehomebuilding.com/project-guides/insulation/simple-air-sealed-ceiling-for-a-high-performance-home So much less to air-seal and can actually be worked on after the insulation is installed. What I like about it is that it is that framing crews know how to frame a second floor, know how to seal Zip, the energy heel truss is there and the rafters are integral (and not applied as with roofline approaches).
Thoughts on that article, Martin?
James,
Josh Edmond's method (framing the ceiling with I-joists and using exterior Zip sheathing as the attic subfloor) certainly works, and has the added benefit of creating a service cavity for wiring and perhaps ducts. (For more on service cavities, see "Service Cavities for Wiring and Plumbing.") But all that extra framing and sheathing is expensive.
Unless you have a fat budget, you're likely to prefer the traditional approach: use the ceiling drywall as your air barrier (paying attention to seams where drywall meets partition top plates, as well as all the usual penetrations at electrical boxes and plumbing vents), and install cellulose above the drywall. There is nothing wrong with burying your electrical cables with cellulose -- builders do that all the time.
Thanks Martin,
I think my sticking point with not using a ceiling service cavity is experience in renovation ... but also working in a house that hasn't followed your other rules and so has a terribly cut up attic without energy heels in the trusses/rafter framing. That makes it so hard to get wiring in outside walls, and to see anything that is going on, so I yearn for inside service cavities. I doubt that an electrician working on adding a light switch is going to clear all the cellulose and adequately seal their new penetration in the top plates. But then again, they could not realize there was a service cavity in the first place!
I'd strongly value disentangling the layers here, so that insulation is separate from wiring, ducts, and water lines.
Although I do wonder about the trade off between services accessible above, albeit buried in cellulose, and the potentially extensive drywall fixing issues that any post-building work implies (with all that dust falling on furniture!). That seems to argue for a conditioned attic with insulation at the roofline.
I shoudl think an even bigger concern is HVAC equipment and ducting in an unconditioned attic . (And if you sue flex duct-if you bury the flex duct in cellulose,- thi sstuff is flimsy-it WILL start leaking within 20-30 years even if mice don’t chew on it !)
I guess the assumption is you are using minsplits ? But seriously, many families (and GBA readers are doubtlessly well above the average income in the USA) are not content with 1,000 SF per floor (dont hate me) I just dont se how you get a larger house “right:” with only two mini split systems (which by the way are now costing as much if not more than ducted heat pumps) you need ceiling fans, open doors most of the time, and limited glazing as no “washing” effect. And when you add in the Maintainence -advocates dont mention taking these units apart and cleaning filters do they ??and ugly -yes truly ugly- wall units, I just dotn get the appeal fo minisplist in all but the smallest and tightest of houses with very open floor plans vs a ducted heat pump system with inverter compressor variable speeds and fans
To do a blower door test on a partially completed house, the ceiling needs to be sheetrocked, taped and all penetrations sealed, but the walls need to be open to inspection. That breaks the drywall installation into two parts and complicates the contractor's scheduling. The connection between the lid drywall and the exterior wall needs careful sealing.
This approach is much cheaper than adding an additional service cavity under the trusses.
Great to start the month with a large serving of Martin's hard-earned experience.
One thing that's worth doing if you are planning a small house is to anticipate how it can change or be expanded over time. Thinking about how a possible stage two and three might look is time well spent, and accounting for these later changes when sizing things like septic fields and mechanical systems, or locating electrical service, makes them much easier down the road.
Totally agree with planning for expansion. Consider an addition on one side of the house, finishing above the garage (or in the basement), or leaving the upstairs unfinished for now. This is especially important if you are an owner-builder, to keep to a reasonable schedule for completion. (After moving in and getting a mortgage, you can continue the work at a slower pace while holding a salaried job.)
As an owner-builder who could do all the work myself, I did the minimum to get a Certificate of Occupancy to live in a planned 3BR 1 bath house with 2 car attached garage. Floors were unfinished (no carpets, tile, finish wood floors) with some items not done (rough-in plumbing was done for a half bath, but unfinished and used was a storage room temporarily). Room over garage not done, but finished later. Addition planned for expanding later to add an ensuite bedroom, formal entry/living room/dining room later. Most interior and closet doors added later, no baseboard or window trim until later. Upper kitchen cabinets not done (I was building cabinets myself), no wall ovens or stovetop, used a hotplate for a stove, I even didn't finish drywall work until later. (Girlfriend insisted on washer/dryer so that was the next appliances after a refrigerator! Gotta have some flexibility to meet your own priorities...). But I got the occupancy permit in one year doing 80% of the labor myself. You can do something similar if you are strapped for funds or time.
Robert,
The downside can be that you may end up like me and have a half finished kitchen for decades. (It's on the list for next summer....)
Malcolm,
But just think about all those nice luxurious kitchens you've built for others! ;-)
I've been in Malcolm's camp. Our last house wasn't finished until the week before we closed on its sale. The wife is insisting on a finished house from the beginning for our next one. Smaller is definitely better.
Peter,
If you are bored sometime and want something to do, I've still got a couple of short runs of baseboard waiting to be installed in the dining room. It's only been 20 some-odd years...
I would add...if you live in a cold winter climate, and your winter climate is moderately sunny (e.g., dry cold winter climates, east side of the Rocky Mountains, Northeast US coast), and if your building lot provides a clear view of the sky to the south (no nearby buildings or tall trees--at most half the height of the distance to reach them from your building site), then you are lucky and you can:
1. Try to have your home with the longest sides facing south/north (and shorter sides facing east/west) to get more sunlight on the south side in winter, and less sunlight beating on your house and west and east windows in the hot summer (as Martin mentioned).
2. You will get LOTS more sunlight in the winter (providing free and nice daylighting and solar heat gain during those dark and cold winter days) from south-facing windows (about three times as much as east & west, and 15 times as much vs. north).
4. Try to put more/larger windows on the south, and fewer/smaller on the west. It will reduce your heating bills in winter, and reduce your cooling bills in summer, not to mention making your home more comfortable.
5. Don't go overboard with too much south-facing glazing area or eliminating west-facing glazing. You don't need to build a passive solar home to benefit from designing your home to be in sync with your climate. You can calculate the solar heat gains if you wish. This is SUPPOSED to be done per room/area when you size your heating system, but most HVAC companies just suggest/install a heating system that's way oversized. Oversized systems cost more, and overshoot/undershoot your thermostat setting vs. correctly sized systems.
6. P.S. - Winter sunlight is free heating, and helps reduce global warming heating and cooling system alternatives. And its free daylighting as well. Avoiding summer solar heat gain is equivalent to free A/C, reducing the need for A/C to keep your home comfortable, and helps reduce global warming from using energy on AC cooling systems. Its a shame to design a home that will need more heating and cooling, not to mention paying those utility bills and increased costs of heating/air-conditioning systems.
7. Most people need to see more daylight in winter. Not just to get some vitamin D outdoors. Some experience "the winter blues" or even Seasonal Affective Disorder during the dark cold winter months. So for some people, its not just about saving money or saving the planet. Its about enhancing mood and avoiding seasonal depression.
8. For those in hot southern climates, you want to attempt to have more north-facing windows, and less west (and east) facing windows to avoid solar heat gain. Unless your home is shaded by nearby buildings or large stands of trees.
For more details on climate and solar heat gains, see this article:
https://www.greenbuildingadvisor.com/article/a-quantitative-look-at-solar-heat-gain
I complete agree. I live in a cold climate and the long sides of my house face south/north. I have high solar heat gain triple pane windows that let in lots of warm sunlight in the winter. From November to April I turn off the heat pumps during the day and sun heat the house. Nothing like the warmth of the sun in the wintertime to drive away those blues. I do have shades on all my windows which do a good job of keeping the house from overheating in the shoulder months.
“[Deleted]”
This is all great advice. The only thing I wonder about is backup heating in an all electric house in a cold climate, in a region where power outages are common. A well insulated tight house can go for days without freezing, but what if the outage lasts longer? A wood stove for that purpose might not be such a bad idea. The other option is a propane tank, feeding a vented propane heater, or feeding a generator.
Do you mean to be recommending one of those in particular?
Charlie,
Almost every house in the U.S. has a central heating system that stops working when the power goes out. That applies to almost all furnaces or boilers that burn oil, natural gas, or propane, as well as to air-source heat pumps.
If you want a system that works without electricity, your two suggestions -- a wood stove or a propane heater with through-the-wall venting (a model that doesn't require electricity) -- make sense. But if you are concerned about global climate change -- and presumably, all green builders are -- you won't want to run these backup systems very often.
Charlie: We've had no problems running our mini splits with a 7000 watt Honda gasoline generator. It'll even run the electric resistance water heater if we don't operate much else at the same time.
The generator plugs into an outside receptacle that is wired to the electric panel. Of course there's a provision preventing any backfeeding to the grid.
The importance of a home that the owner loves and fits their lifestyle can't be stressed enough. I would argue that 90% of all design mistakes are typically made in the first 10% of the work. Wrong place for the building, wrong orientation, wrong layout of interior space. As always Martin, wise words. And when all may be lost, a beer may help.
Scott,
Although architects have filled the air for centuries with manifestos and theories, I think it fell to Joe Lstiburek to put it best:
"I think buildings should last a long time. Over my half century and then some of existence on this blue spinning celestial ball, I have learned, mostly the hard way, that in order for buildings to last a long time, people have to take care of them. Now, in order for people to take care of them, people have to want to take care of them. And guess what? People don’t take care of ugly things. Ugliness is not sustainable. People need to want to live in a building and work in a building. Only then will they take care of it. That is why beautiful buildings are important. That is why architecture is important. I think we should have beautiful buildings. I think they should also be safe, durable, comfortable and energy efficient. Note that the energy efficiency part is at the end of the list. Nowhere do I mention the words green or sustainable because the terms are too general to be meaningful to me."
Malcolm,
Thanks for your comment. You're absolutely correct, of course, that Joe Lstiburek's writings and statements on the connection between the beauty of a building and our willingness to maintain a building have informed my beliefs. Lstiburek is due a citation on this point, and I regret my failure to cite him. I have edited my article to correct my omission.
Again, thanks.
Great list Martin, and I appreciate your acknowledgement that homes in warm climates exist and have different needs than those of you in the tundra.
One thing I think you missed here is NOT using heat pump water heater in colder climates. I heat for about 10 months out of the year, so that would be 10 months where the water heater is cooling the house, fighting the heating system. And generally, water heater heat pumps can't work from low-temp air, so no using outside air. My situation is not super-common, but it's worth explaining to people that the heat pump water heater will essentially be cooling the room it is in.
We went into this in great detail in this thread:
https://www.greenbuildingadvisor.com/question/where-is-the-most-efficient-place-to-get-the-heat-for-hot-water-from
The answer depends on where the alternative is for getting the heat for the hot water from. For example, if you're heating the house with gas, and the choice is heating the hot water with gas or with a heat pump, yeah, with a heat pump all the heat for the hot water is coming from the gas heat and if you just heated it directly with gas you'd be saving all the electricity the heat pump uses.
But if you're heating house with a heat pump, and the choice is heating the water with resistance electricity or a heat pump, the heat pump saves electricity over resistance.
Sribe,
You wrote, "The heat pump water heater will essentially be cooling the room it is in."
You're right, of course, and I've explained that fact many times in other articles. This article isn't comprehensive; anyone uncertain of which water heater to choose should, of course, perform more research than simply reading this overview article. See, for example:
1. "Heat Pump Water Heater Brands" in which I wrote, "Remember, a heat pump water heater will lower the air temperature of the room where it is installed. "
2. "Heat-Pump Water Heaters Come of Age" in which I wrote, "The temperature of the room in which the [heat-pump water heater] unit is installed will drop when it is operating, by anywhere from 2 F° to 6 F° — and perhaps even more during heavy draws of hot water."
3. "Attaching Ducts to a Heat-Pump Water Heater" in which I wrote, "The [water-heating] process also cools the air in the room where the heat-pump water heater is located."
Oh, I know you know it ;-) I was just suggesting a simple one-sentence call-out to be careful and do research in cold climates.
Sribe,
I know that heat-pump water heaters make sense in many c0ld climates, including Vermont. Where do you live? Even if you have a few days of space heating in May, June, and September, it's unusual to need space heating for every day in May, June, and September.
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