Comment by dredmorbius | Hacker News Reader

Comment by dredmorbius | Hacker News Reader

Spot-heating, especially within a leaky building envelope utilizing expensive heat sources (electric resistance) is one option.

But it's hardly the only one, or the best. For northern climates, taking a whole-system approach to home/structure design gets you a tremendously greater payoff in terms of energy savings.

Among the most powerful demonstrations of this I've seen are Thorsten Chlupp / Reina LLC's experiences designing and building zero net energy homes in Fairbanks, Alaska.

His videos are long (~90 minutes) be exceptionally comprehensive. The TL;DR is:

• Total envelope. He pays exceptional attention to any thermal envelope penetrations. All emissions (air, water, sewage) pass through thermal exchanges.

• Thermal mass. The foundation, flooring, central masonry stove, and a 5,000 gallon stratified thermal storage tank all store and scavange thermal energy both passively and actively.

• Moisture control. Heat barriers introduce thermal issues. Chlupp makes use of multiple glazings, window setbacks, and _exterior_ thermal shutters to minimize moisture buildup on windows. Moisture barriers and ventilation of interstitial spaces is designed to clear moisture.

• Heat pumps. Rather than create thermal energy directly (other than the masonry stove), Chlupp moves heat using ground-loop heat pumps.

• Solar and net metering. Solar panels (yes, in Alaska) and net metering help him arrive at net zero energy. His first-year goal wasn't met due to plug-in hybrid vehicles, an oversight in his energy modeling.

Though conceived as a whole-system ground-up greenfield design, the principles are applicable to a lesser degree as retrofit options.

Oh, and for heating your bed: a 1 liter Nalgene bottle, filled with boiling hot water, and slipped into a wool sock, will heat your bed cozily. Two are almost certainly too hot, but you're welcome to try. And they'll last the night.

http://www.reina-llc.com/

Alaska's First Net Zero Energy Homes Performance Update http://fixyt.com/watch?v=Xen_VWyDezY

Path to Net Zero Energy Series -- Alaska's first Net Zero Ho... http://fixyt.com/watch?v=AtHkvpRI6fc

http://fixyt.com/search?q=thorsten+chlupp+zero+net+energy

Not to mention:

In a well-insulated, well-designed house, you won't have any worries about frozen pipes, even with a low thermostat temperature, since all pipes will be inside the insulated enclosure.

There's a whole community of people trying to build better buildings out there. The Passivhaus people, the PERSIST (Saskatchewan) and REMOTE (Alaska) approaches (http://www.greenbuildingadvisor.com/blogs/dept/musings/getti...), Building Science Corporation, the NRC in Canada (http://archive.nrc-cnrc.gc.ca/eng/ibp/irc/cbd/digest-index.h...).

Some of these people are ex-hippies or hippie-ish, and there is a bit of bullshit out there, but there's certainly plenty of better ways to build and renovate homes for energy efficiency.

I'm currently living in a passive house (in Belgium, Europe). We've only moved in two months ago so we haven't experienced a winter yet but even in the current summer climate it has already been an order of magnitude more comfortable than any of the other places I've lived in. When the temperature hit 30 degrees Celsius for a couple of days last week the house was at a comfortable 23 degrees. Everywhere.

Key design points:

- Insulation, insulation, insulation. We have 30cm cellulose in the walls and 36cm in the roof plus some 5cm fiberglass in the space between the walls and drywall.

- Airtightness, in combination with a ventilation system (with heat recovery).

- Large windows (triple glazing) on east, south and west sides to get free heat from the sun in the winter but have some screens to keep the sun out in the summer.

- We use a geothermal heat pump to prepare hot water and to be able to heat the house a little bit in the winter when needed, using underfloor heating pipes. Extra bonus that has turned out to be essential: we can use this system to passively cool the house by simply pumping the water through the pipes and into the ground. This can lower the temperature in the house by several degrees in an energy efficient way.

Based on our energy consumption for the two months we've lived here we'll end up at around 3500-4000kWh per year. And that includes everything: heat pump, ventilation, all electrical appliances, ...

Building such a house isn't rocket science. The materials and techniques are well known and readily available (at least here); it's mostly a matter of good planning upfront and paying attention to the details when executing. Not all construction companies are up to speed but they're slowly getting there (or they'll disappear).

As a matter of fact: the EU has mandated that by 2020 every newly built house must be more or less equivalent to a passive house.

Chlupp's design borrows very, very heavily on passive house concepts.

And he uses massive amounts of insulation. He creates a large (big enough to walk in) wall cavity, and fills that with blown cellulose. I think it's on the order of twenty tons of cellulose. Not only does it insulate, but it forms a thermal mass.

Similarly for his foundation: a large sand base as I recall, then a slab, which create yet more thermal mass. The masonry stove at the building core is another, and finally a 5,000 gallon vertically-arranged water tank. This has a perforated distributor, and the idea is that he circulates water through his masonry stove and solar thermal panels whenever the output of those is warmer than the water at some point in the tank -- it tends to be ~120F near the surface, and ~40F near the bottom. The water stratifies according to temperature, and he banks his BTUs.

In our case it's something like five tons of cellulose. It's supposedly a good buffer against summer heat getting into the house but it doesn't really store heat to release it slowly when the temperature goes down again. I can imagine it works well high up north but here I think it would make it more difficult to control the temperature. It's one of the reasons why we have chosen a wood-based construction using I-joints. We do have a concrete foundation slab, screed everywhere and ceramic tiles on the ground floor.

The big stratified water tank is a well known concept but you need to have room for such a big tank. Here in Belgium space is at a premium so houses tend to be on the small side. Solar thermal panels are often connected to a tank of 500 litres or less, simply because of space constraints...

There are several possible construction models; it's a matter of selecting one that fits your local climate and your habits. Not everybody likes a stove for example.

The last couple of years we've seen a shift happening from applying the passive house concepts on new houses (pretty much a solved problem) to renovating existing ones. Here in Belgium there's a massive amount of old houses constructed before the seventies/eighties which is when they finally started putting in insulation. Now that all new houses are energy efficient it's time to tackle the massive waste in those old houses. Most people buy such an old house and start renovating so there's a lot to be gained.

In Chlupp's case, he pretty much designs his structure around the tank, it's integrated to the building core.

An alternative he points to in Europe is a community / neighborhood storage, where a thermal storage tank serves a number of homes. Another option is seasonal thermal storage using ground-base storage, where you've got suitable geology (no moving water table to whisk your heat away helps a lot), used in at least one instance in Canada. Heat is pumped in during the summer and extracted in the winter, as part of a ground-loop heat pump.

> underfloor heating pipes [...] we can use this system to passively cool the house

While floor heating is cozy and wonderful, I am somewhat skeptic on the comfort of floor cooling.

I live in southeast Alaska, where heating issues can make or break your ability to pay rent or afford a mortgage.

Most homes are heated using fuel oil. We moved into an awesome old house last summer, and we were worried about heating costs. The landlord had a heat pump installed last fall. I'm sure we would have had some $300-$500 heating bills (per month) last winter if we were using oil, but the heat pump never cost more than $150 per month.

That was a relief, because we spent one winter in a drafty house with a malfunctioning boiler system. That was not fun at all, and we moved out just because of heating costs.

I'm hoping to buy a house sometime in the next few years, and the first thing I'll do is complete a thorough heating overhaul of the house.

Ground Loop or air to air heatpump? What brand and model?

(I ask because we just bought a house in montana and are thinking about a heatpump before winter...we have propane radiant heat now. We'd want one that would work with cold temps though it rarely gets bellow -10 F here.)

It's an air to air Fujitsu. I'll check on the model when I get a chance.

Most of our winter weather hovers in the mid 30's, day and night. We get occasional cold spells in the 20's, but it's rarely in the teens and I've seen single digits once in twelve years here. I don't think it's ever been below zero here.

It was interesting to get used to the heat pump just being on low all the time. Our monitor stove would come on in bursts, and you'd notice a steady heating/ cooling cycle throughout the day. The heat pump just puts out a steady, slightly warm airflow all day long.

I'm not sure how heat pumps behave in colder climates. Our landlord did not remove the monitor stove when he had the heat pump installed, and it was nice to know we could fall back on the monitor if the heat pump was not putting out enough heat. You might consider leaving the propane system in place this winter if you do try a heat pump. It might just give you a little peace of mind about not having an issue in the middle of a cold spell.

Feel free to send an email if you're curious to ask more.

The model number is ASU15RLS2.

Take a look at the presentations I listed above. Chlupp eliminates the furnace / heating system entirely.

It's one of his design goals. Minimizing your furnace requirements (but not eliminating them) gives you progress, but it remains a major expense (for installation and operation). Eliminating it entirely addresses a huge cost element for northern construction.

I don't live in Alaska myself, and can't speak to the full validity and credibility of his work, though it seems pretty solid. But I'm absolutely impressed with his attention to detail and the specifics of his methods and approaches.

On hot water bottles: the energy spent boiling that water is likely comparable to the energy an electric blanket on low power would use.

Depends: are you using a gas stove, electric stove, inductive stove, or a microwave to boil the water?

Or a kettle.

Boiling water produces a lot of waste heat. I'm inclined to believe an electric blanket is pretty good comparatively.

Of course my house is all electric, so there are no electric vs. natural gas conversions to make.

Wasted heat? All the wasted heat goes into the air, warming up the room.

The room being the kitchen, which is not the room you're trying to heat up as you prepare for bed.

The egress path of that heat will tend to be dissipation throughout the habitable area, modulo circulation. One factor I've noted in room heating is how much heat tends to rise toward the ceiling. A vertically-oriented fan (need not be a ceiling fan) will help achieve a good blend of temperature floor-to-ceiling.

Air flows between rooms / through doorways can also be surprisingly stubborn, but it does happen.

The specifics will depend on the size of the interior space, position of the kitchen, access to exterior walls, etc.

Don't use boiling water with hot water bottles; the ones you can buy have warnings about this (it can damage them). Just use hot water from the tap (which hopefully should be more efficiently heated than however you boil water as well).

Don't worry about energy consumption; it's negligible for the hot water bottle, and for the electric blanket as well, especially compared to keeping your house heat up high at night. Not really worth debating, though do note: the hot water bottle has a fail-proof, gradual, automatic shutoff, it fits any size bed, requires no electric outlet, requires minimal storage space during warmer months (so you can have an extra for guests), and has an initial investment of, like, $4. :)

If the bottles are dedicated to this use, it's fine.

The soft-walled ones may discolour slightly.

It probably depends on the water bottle.

I put boiling water into a fairly thin-walled rubber one, and it sprang a leak a few minutes later, so I'm more careful now.

There's a reason I specified Nalgene.

Electric blankets can burn you and the whole house down and do not use the same form of heat transfer https://en.wikipedia.org/wiki/Heat_transfer. They just should not be used.

> Electric blankets can burn you and the whole house down and do not use the same form of heat transfer

Source on that? I had a quick search, and it seems to be one of those rumours... The only reference I could find was old (pre 2001) and faulty models.

There are gel filled alternatives that can be heated in the microwave. No idea if they retain their heat as long.

Any thermal mass will do.

What I've found is that a liter bottle packs a goodly amount of heat, the sock regulates the release just about perfectly (and keeps you from scalding yourself against it), and the result is quite toasty. There's also nothing quite like having warm toes in bed.

The bottles are still warm in the morning under a good duvet.

The thing about bottles is that they're cheap, multi-purpose, very specific, don't have cords, pose no fire / tripping / electrocution risk, can be moved about, etc., etc.

A highly effective low-tech solution.

Yes, the efficiency of heating the water in the first place may vary, though that's energy that's almost certainly delivered to your residence space, so in that regard it's pretty much a wash.

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