[1] https://www.health.ny.gov/publications/6594/
[2] https://www.cdc.gov/disasters/extremeheat/faq.html
[3] https://sci-hub.st/https://pubmed.ncbi.nlm.nih.gov/31382270/
Here's the magic trick to cool your home down quickly:
During the day your house heats up. In the evening your home is likely warmer than the night air. Many people try to open the window and put the fan close to the window to blow cold air in.
What works much better is pointing the fan out of the window!
Not only did it quickly replace the indoor air with cooler outside air, it would also ventilate the attic, preventing it from quickly reheating the upstairs. I could run it for 5 minutes and get the desired effect, maybe 10 minutes in an unusually hot spell.
Not unless you wake at 3AM to implement it. In summer, by the time most people go to bed the temperature has not dropped significantly yet.
Where are you talking about?
I used the technique I described in eg London, Sydney and parts of Germany. Most of the time, temperatures had dropped quite a bit by 22:00. (But not always.)
Now I live in a cooler climate. The highs can still get as high in the day, but it does cool of at night - nearly as soon as the sun goes down.
Such a system is basically a mold incubator. The correct method is to:
1) have central HVAC
2) have an energy recovering ventilator (ERV), zhender is a good brand.
#2 Constantly cycles fresh air throughout your home and it’s intake is controllable and filtered.
My suggestion was for situations like London or Germany in summer. The air cools down a lot in the evening there, and people typically don't have any A/C there nor humidity problems in summer. The point-fan-out-the-window technique is for rapidly bringing your home down to ambient temperatures (and humidities).
There will be no condensation, and thus no mold, because the ambient night air is above its dew point, and your own walls start out hotter than the ambient air, and they only approach its temperature _from above_ as you ventilate the house.
What you are describing sounds like it might be more appropriate for something like Florida.
In places like Germany or London, people have mold problems in winter, when the walls are colder than the air in the home.
(You can also get mold problems, when you are running an AC.)
From my travels around western europe I also noticed a SHOCKING number of bathrooms lack any form of bathroom fan, so hot showers spike the indoor humidity and it stays there.
>The point-fan-out-the-window technique is for rapidly bringing your home down to ambient temperatures (and humidities).
Sure, but the goal is to do that in a controlled manner. Every outlet needs an inlet, and that inlet can either be a dedicated one with a filter (via ERV) or cracks, crevices, and air leaks around your house that you can't see. By puling in uncontrolled outside air you risk moisture buildup in those areas that can lead to mold and rot.
>There will be no condensation, and thus no mold, because the ambient night air is above its dew point, and your own walls start out hotter than the ambient air, and they only approach its temperature _from above_ as you ventilate the house.
Unless your interior air is humid, because the house lacks even the most basic form of humidity control. Then those air leak spots cool the area they're leaking in around which then makes condensation from your interior humidity.
>(You can also get mold problems, when you are running an AC.)
Oh for sure. My point is that a house with proper AC, humidity control, and ERV will be extremely resistant to mold growth. It will also feel fresh, comfortable, you'll sleep better etc.
(In Germany, problems with mold were usually in winter, anyway.)
Yes, bathrooms with neither windows nor fans are annoying.
> Sure, but the goal is to do that in a controlled manner. Every outlet needs an inlet, and that inlet can either be a dedicated one with a filter (via ERV) or cracks, crevices, and air leaks around your house that you can't see. By puling in uncontrolled outside air you risk moisture buildup in those areas that can lead to mold and rot.
Eh, the air will mostly be pulled in either through another open window (good), or through the same window you are blasting the hot air out of (slightly less good), because your fan doesn't form a seal.
I don't really see how you are getting your moisture build-up. You only really get condensation on the walls, when your walls are colder than the air.
> Unless your interior air is humid, because the house lacks even the most basic form of humidity control. Then those air leak spots cool the area they're leaking in around which then makes condensation from your interior humidity.
I never heard of anyone having that problem in summer, and never had it myself.
I have no clue where you are taking your worries from.
The silver lining is that it will get better eventually since bugs are dying off rapidly but for now it's either eye strain or buying nets for every window.
I just remember: hot goes to cold. So pushing the hot air toward the cold air is more efficient. If that means pushing the hot air inside the home toward the outside then sobeit.
If you have a multistory house you can open windows at the top and bottom, the warm air will tend to flow out and pull cool air in the bottom. In that situation if you have a fan, it would make sense to have it blowing air in on the lower level, or out on the upper level.
If you have a single level, the fan will just create a slight pressure difference in one direction or the other. You just need to open several windows, preferably on opposite sides of the room, and if you use a fan to pull cool air in that creates a positive pressure inside the room, which will force the warm air to be exhausted through the other open windows. If the fan is blowing warm air out, then the room pressure will be negative relative to the outside, and cool air will be pulled in through the other open windows.
Getting a draft through your entire place is also good.
What I suggest with the fan works, when you can't do either of the two above.
> I don't see that it matters much which way the fan is blowing. What matters is the air exchange, which is about creating an airflow.
The latter explains the former. A simple experiment: sit 2m in front of a running fan, then sit 2m behind a running fan. In front, you will feel lots of airflow, behind you will feel almost nothing.
That's because the fan 'pulls' air in a diffuse manner, but pushes it as a directed bundle.
It's probably equally as effective to put your fan outside the home and point it inwards, or to put it inwards the home and point it outwards. Alas, most people can only put the fan _inside_ their home, perhaps at the window at best. But that's less effective at exchanging air with the outside than pointing it outwards.
> If you have a single level, the fan will just create a slight pressure difference in one direction or the other. You just need to open several windows, preferably on opposite sides of the room, and if you use a fan to pull cool air in that creates a positive pressure inside the room, which will force the warm air to be exhausted through the other open windows. If the fan is blowing warm air out, then the room pressure will be negative relative to the outside, and cool air will be pulled in through the other open windows.
To use your terminology: the fan is better at pushing air in a concrete direction, than at pulling air from a specific direction.
Result: the longer I let the fan run, the hotter the inside got. I saw the thermometer rise from 22.1 to 22.4.
Your results seem rather strange, though. I wonder where the extra heat came from? Thermodynamics say that heat moves from hot to cold places, unless something intervenes.
I think it's good at keeping heat out, but the house itself contains a lot of heat producing things. Any appliance and creature produces heat.
If you do, you get A/C for 'free', and if you don't, you're wasting so much energy in the winter that you can never make up for it by 'making do' with a fan rather than proper air conditioning.
Signed, some guy who was in Belgium for the heat wave in 2018 and thinks Europeans should just suck it up and put in heat pumps. Sweltering in the summer and burning gas directly in the winter isn't virtuous.
This startup has a neat idea, and I hope to see more about it - https://www.gradientcomfort.com/ - but $2000 feels like it's not competitive.
And if anyone happens to know of one (and not an AC that will just do electric heat) available in the USA, I'd be grateful to hear about it. Amana will sell me one - for $1300 for 12K BTU, and that sounds...high.
I probably can’t make it work, because I need a bit too high water circulation temps to meet the heating load at 12°F/-11°C and the up-front economics are significantly worse due to not enough experienced installers/general lack of competition in the air-to-water space. (Our gas prices are low enough and electricity high enough that the payback period is lengthy.)
If I had existing ducts, air-to-air heat pumps would make a lot of sense (and would give AC automatically), but hydronic distribution doesn’t afford “free” AC.
If you use glycol, you’d typically use a plate heat exchanger inside and still use water as the main hydronic distribution medium (out to radiators in my case or to floor warming in other installs), but this gives up a small amount of efficiency and some maximum heating capacity. (If the max leaving glycol temp is 130°F/55°C, your max water temp will be a few degrees below that after the heat exchanger.)
The split units (refrigerant lines in/out of the building) can go directly to water, meaning a max leaving temp of 130°F can go directly to the radiator loops.
I get the sense that you've evaluated this thoroughly and it actually won't work for you, that does happen.
We get bitter cold as well as sultry summers, and I have an AC which I keep thinking about replacing with a heat pump, just because it bothers me aesthetically that I can't run it backward for the intermediate months when it's cold but not that cold. The bill would be cheaper but the depreciation on replacing a perfectly good AC would take a long time to balance.
In terms of “can it work for me?” it’s like most things: if you hit it hard enough, it’ll fit, but the low cost of replacing a boiler with a boiler, the high cost of electricity in MA, and the dearth of A2W heat pump companies (both competing to supply equipment in the US and locally installing) makes it uneconomical, not thermodynamically impossible. (It’s right on the edge but inside of the latter; via experimentation this winter, I determined that my 2 lower levels can maintain temp down to 10°F with a leaving water temp cycling between 125-135°F, while the converted attic needs 135-145°F at 10°F OAT. Most A2W heat pumps max out at 55°C/130°F leaving water temp, and even at that level are necessarily giving up efficiency and heating capacity as compared to a 45°C or 50°C LWT.)
Obviously, improving insulation would change those figures, but in a structural brick house with complex interior wall finishes, adding radiation in the attic and supplementing the heat pump with an electric boiler below 15°F OAT would be wildly cheaper, especially since the COP at those temps is well under 2 and the runtimes under 15°F would only be around 50-75 hours per year.
It could work, and would allow us to get rid of local fuel combustion entirely, but even after a $10K government incentive, it would be at a cost that is still a multiple of what gas-for-gas replacement ($2.5K government incentive) and running for 15 years would cost and with the risk of having an uncommon system that only a few companies understand and can service. Perhaps the boiler after this next one will be replaced by a heat pump; I hope things develop in that direction.
We may end up adding some mini-split (air-air) heat pumps, mostly to provide AC and dehumidification in the summer (replacing window shaker units), but those would also be quite economical to heat with in the long shoulder season (40-60°F OATs).
Eh, depends on what you are heating with in winter.
A friend of mine lives in a rural area and basically gets firewood for free. Even the best heat pump can't beat that.
(Heat pumps are still great in general. And much better than using electricity directly to heat.)
There's something satisfying about trading labor directly for something like heat that you normally have to buy. Exercise is good for you, sustainability and resilience are virtues, and so on.
But heating even a modest space with wood is a Lot of Work.
Also, it's still quite energetically inefficient, but that's a technicality here I feel, energy isn't completely fungible (it does salvage my sentence, which was about energy). The carbon accounting would be interesting to spitball but fiendishly hard to do fairly.
Moving air also helps against mosquitoes, I have read!
Not being able to heat a room above 16°C is a better problem to have than not being able to cool below 30°C but cold takes it's tool too. At night you can use a thick comforter or a couple and the problem is solved, but working behind a desk in a cold room is trying. Many layers of closing helps but it is not an ultimate answer - while being in a cold room in warm clothing I become tired more quickly than in a room at 20°C—25°C.