Hacker News Reader

Comment by DavidPeiffer | Hacker News Reader

I'd suggest people research whole house fans. They mount in the ceiling on your top level and suck air from your open windows into the attic.

We had one growing up in Iowa. Despite upper 70's to mid 80's much of May, June, and July, we were able to avoid running the air conditioner by sucking in the 50-60 degree air overnight and closing up the windows during the day. By late July and August, it was time to use the air conditioner.

The fans can typically rotate all the air in a house every handful of minutes, and the breeze helps sweat evaporate, immensely helping comfort. Their cost is typically a couple hundred dollars, but you can spend up to ~1,200 for a quiet, high volume model.

I'm looking to install one in my house. The downside I'm trying to work through is, should a fire break out, I want the fan to turn off. I haven't found a COTS system to do this and integrate with the hardwired smoke detectors.

View on HN

Another down side is, you don't want to do this if you're in the swampy south. You'll bring in all the humidity and that will cause all sorts of problems. Also, you bring in any dust, pollen, etc that may be lingering.

Putting air purifiers by windows could probably help. Might need a couple though. It might work with just one big though, for instance I know there's huge tube shaped ones with a ton of surface area to catch stuff in HEPA- or electro static filters.

This works great for me in NE USA. We have two large filters. Usually keep one upstairs and one downstairs. They make a noticeable difference. But they were about $250 each.

To counter matt_the_bass's example, I live in the NE US, I have always used the method (in this case, window upstairs open, window downstairs open, natural draft cooling the house by dragging the air through), but there is absolutely no level of filtering that will stop all pollutants and allergens from entering the house as long as you are not filtering 100% of the air.

Last time I noticed, nobody makes a window-sized AC-esque filter that works efficiently down to PM2.5 levels... and doing so would also eliminate said window being a window.

This was a pleasant surprise for me to read. My father installed one in our home in Ohio in the late 60’s and it worked great.

My dad was ahead of his time. He installed a geothermal heat pump to heat the house with heat from our 200’ well, too.

Thanks for a pleasant reminder!

You need a smoke detector that provides dry contacts/relay output and some minimal wiring.

Thank you, I was coming up short on terminology since this is outside my normal field! It looks like there are some relays directly from Kidee which might integrate directly with the hardwired smoke detectors. I'll definitely do some more research.

Dear god, I thought that fan idea sounded awesome until you mentioned the fire concern. Good thing you’re smart and thought of that.

Life involves risk. We also suck at evaluating risk, and statistics are helpful to a point. You only have one life to live. Life insurance companies spread the everyday risks across many people.

Fires spread much faster than they used to because of changes in building materials [1]. I figure if I can find a way to shut it off automatically, it'll buy me 30+ seconds, which is a big deal.

I found [2] awhile back, which is what I want, but I'd happily pay for a COTS solution.

[1] https://youtu.be/aDNPhq5ggoE

[2] https://hackaday.io/project/165689-prevent-accidental-3d-pri...

Looks like [1] addresses the furnishings in the room, not the building materials. Modern drywall, for example, takes 30 minutes to burn. And fire rated drywall takes an hour.

Brick and mortar takes a lot longer than 30 minutes to burn.

Yet has decidedly more 'fall on my head in event of an earthquake' potential than stick building, in my part of the world. Different building materials have trade offs.

Plus, how many residences (other than chic converted factory lofts I guess) even have bare brick and mortar interiors?

Interesting. So essentially the same as having fans in your windows, but without all of the noise (since one powerful fan in a central location is pulling air out of the house)

Yep. Growing up it was a 36" direct drive motor attached to the fan blades. It was a louder unit, but that was fine since it was in the back of the house away from bedrooms. There are quieter units available which are driven by DC motors with additional sound isolation features available, such as https://quietcoolsystems.com/whole-house-fan/. Probably the direction I will go when I install one.

You’ll need the equivalent of this for your brand of smoke detectors:

https://support.firstalert.com/s/article/rm4

And, depending on whether your fan is in spec for the built in relay, you may need a larger relay to switch it.

We had one of those in the house when I was a kid; we called it the attic fan. It was noisy and generated a noticeable breeze in the house, but we had it for warm days and window a/c units on hot day, until dad got central air installed when I was in high school.

There’s also radon to consider… yikes!

Best treatment of radon is a lot of fresh air exchange. It's what these fans do well.

The fan wouldn’t be exchanging fresh air, it would be drawing it up from the ground. Radon gas is a product of decaying uranium underground. It usually gets into homes due to the “stack effect” where heated indoor air rises (in winter) and draws the gas up through the foundation. The parent commenter seems to be proposing a mechanism to do this in summer as well, just using a fan instead.

You open the windows in the house when running the whole house fan.

When we installed the fan, the documentation mentioned failure to open 9 square feet or more of outside doors/windows could result in a window breaking from the negative pressure.

Like someone else said, you open the windows.

A negative pressure house is bad for more than just radon. It can cause certain appliances to vent bad stuff into the house too.

Would you eventually suck them dry of bad stuff? Would putting appliances in a negative pressure environment before selling them to consumers be good?

"bad stuff" in this case is combustion gas from natural gas appliances, sewer gas from sucking the water out of toilets, etc. So no, there's no end to the "bad stuff" they generate.

Separately, offgassing is an issue for sofas and mattresses, anything made of particle board as well, but if you put them in a low pressure environment, it doesn't drastically accelerate offgassing. If they offgas formaldehyde, they're going to keep doing it after the low pressure period has ended, so better to avoid those materials altogether.

We have a radon meter in the house. Even just a single box fan in Window, sucking air out of the house makes and ENORMOUS difference. We're talking <1 ppm, whereas before it could get up to ~12ppm on bad days. We bought a radon removal system when we bought the house, it it doesn't seem to work nearly as well as simply venting the house.

Radon is particularly prevalent in Iowa. A completely closed up house is the worst thing for it!

My dad spent a few years thinking through details about the house before building. Passive radon mitigation was built in (active added later), air exchanger would bring in new air without losing all the heat/cold of the conditioned air, radiant floor heating in the basement, ~24" of blown in insulation in the attic, 6" walls for additional insulation, 24" eves give a bit more shade around the house.

Yes. First get a sensor so you can track it, radon can change quite a bit over time. I bought two from airthings.com. They support IOS, Android, and even have an graphana plugin (direct, not requiring upload to a cloud first). They track temp, humidity, VOCs, radon, CO2, and something else I can't remember. They have pretty incredible bluetooth range, it's slow, but I can get an update of both sensors from anywhere in my 3 story house. I'm used to bluetooth only sometimes working when on the same floor.

After mapping out my house we saw numbers as high as 15, 4.0 is the recommended mitigation threshold in the USA, 2.6 for the EU.

After talking to a company they recommended sealing our sump pump area, and then installing a fan that sucked air from under our foundation. Our readings dropped from 15 to 0.5, and stayed there. I do wonder how long the sump pump sealant will last, but I have the airthings to watch.

So sure, open up the windows when you can, but I'm glad I can close the windows when it's smokey or cold and still have low radon levels.

Reply on news.ycombinator.com