Author Topic: I have built a whole house fan!  (Read 10910 times)

Syonyk

  • Magnum Stache
  • ******
  • Posts: 4610
    • Syonyk's Project Blog
I have built a whole house fan!
« on: March 23, 2015, 10:36:45 PM »
In a rental.

That only has sideways-opening windows upstairs.

Two pieces of aluminum L bracket, 6 Delta 120mm fans with grates, a 12v PSU, some 3M double sided sticky tape (car-trim brand stuff - expensive, but by far the nicest double sided adhesive I've used), and a fan adapter I had laying around.

650CFM in open air, which even fighting against house draw with windows open should be 300CFM.  My house is ~10500 cubic feet total, so with this rack on, I can, in theory, do a full air exchange every 35 minutes (at 50% derating for pressure).

All for... um... about $200. :/  But it should last forever.

And it's flexible enough to use in other houses down the road.

http://syonyk.blogspot.com/2015/05/house-fan-for-vertical-windows-diy.html
« Last Edit: May 20, 2015, 02:30:48 PM by Syonyk »

CowboyAndIndian

  • Handlebar Stache
  • *****
  • Posts: 1934
  • Location: NJ, USA
    • KOWines: Deep discount wine/spirits store.
Re: I have built a whole house fan!
« Reply #1 on: March 24, 2015, 08:00:05 AM »
Nice,

You could also do this with a box fan for a lot cheaper ($20 and no need for a 12 V power supply).

Syonyk

  • Magnum Stache
  • ******
  • Posts: 4610
    • Syonyk's Project Blog
Re: I have built a whole house fan!
« Reply #2 on: March 24, 2015, 08:21:58 AM »
Nice,

You could also do this with a box fan for a lot cheaper ($20 and no need for a 12 V power supply).

I'm actually replacing several years of failure with box fans.  Box fans have little to no static pressure capability, and the "hot corner" of my house (sun in the afternoon + office thermal loads) has a window that opens into the prevailing breeze, so I have to force air out against the wind (or shove heated air from this room through the whole upstairs).  Several years of attempting to do this (exhaust air) with a box fan have been almost entirely unsuccessful, and that corner of the house tends towards "Uninhabitably hot" a few weeks of the year.  It wasn't a huge issue in previous years (servers beeping from the heat is a little bit annoying, but I can shut them down), but this year I've got my ferrets up there (their room was taken over for a child), so letting it get that hot is dangerous to them.

This way, I can exhaust air from the hottest room in the house, with enough pressure capability to pull cool air up from downstairs (which works wonderfully - I've confirmed it will exhaust air against a decent breeze), and also to suck cool air in from some of the shaded corners of my yard by opening certain windows downstairs.  By running these at night and pulling cool air through, I should be able to chill the house enough (I have no AC) to keep it comfortable through the afternoon, and if it gets really hot in the office corner, I can at least exhaust the hot air during the afternoon and get a breeze in the house, instead of having stagnant hot air sitting.

In previous years, the house has tended towards a nice cool downstairs (shaded, thermally connected to the ground) and an upstairs that's ~20F hotter, stagnant, and even with fans in the windows, I can't manage much but pushing hot air around upstairs - and box fans won't build enough pressure to force much hot air downstairs (that, also, being somewhat counterproductive - forcing hot air through the house to cool things down).

The "right" solution is a whole house fan exhausting into the attic, but, sadly, I rent, and my landlord has no interest in such things.

m8547

  • Bristles
  • ***
  • Posts: 305
Re: I have built a whole house fan!
« Reply #3 on: March 24, 2015, 10:18:18 PM »
I want to do the exact same thing!

I have a small collection (about six or seven) of 92mm x 1.5" Delta fans that I salvaged from old Dell computers and servers. They spin really fast! https://www.youtube.com/watch?v=iDYOh9RrLVE

I've used a box fan in the window, but part of the blade broke when some wind knocked it down. I rebalanced it by sticking some duct tape on the broken blade to add weight, but it makes an annoying clicking sound on low, and it's kind of loud on high.

I live on a busy street, and the noise from cars is really annoying in the summer. I want to build some kind of large scale muffler that allows air to flow but doesn't pass as much sound. It's also dry where I live, so there's a lot of dust and pollen that I'd like to filter out. I also want to be able to close the blinds and still get fresh air since this is in my bedroom. I rent a house with no A/C, and I don't mind it as long as I can get fresh air.

I envision a piece of plywood or similar material in the window with these fans mounted in it. There will be a filter on the outside of the fans, and some kind of duct or baffle system to move air but reduce noise. Maybe I could run a duct to the floor and have a muffler on the floor. It could be a wooden box with baffles that reflect/absorb sound.  Reducing the noise from the fans themselves is probably the most difficult part, since they are much louder than traffic.

Syonyk

  • Magnum Stache
  • ******
  • Posts: 4610
    • Syonyk's Project Blog
Re: I have built a whole house fan!
« Reply #4 on: March 24, 2015, 11:03:12 PM »
Muffling those will be hard.  Your best bet is to stick them somewhere else in the house, exhausting, and have an intake in your bedroom with a furnace filter & some foam baffles to muffle sound.

Syonyk

  • Magnum Stache
  • ******
  • Posts: 4610
    • Syonyk's Project Blog
Re: I have built a whole house fan!
« Reply #5 on: March 26, 2015, 01:58:42 PM »
Updated photos, now with cable management. :)

It's purring away nicely, venting the house.  It's certainly noticeable 2.5' away from my head, but it's not actually that loud.

bzzzt

  • Bristles
  • ***
  • Posts: 303
  • Location: Chicago
  • 5v to Lightning Bolts...
Re: I have built a whole house fan!
« Reply #6 on: March 30, 2015, 06:45:26 PM »
If noise eventually does become an issue, double the fans but run them on +7v (tie +12v and +5v feeds together). I used to do it a lot when I was in to overclocking processors/GPUs back in the day. My mom hated the "vacuum cleaner" coming from my room (a few 60mm and 80mm Deltas), so it was necessary when I wasn't using it. Those were the days before shrouds for 92mm and 120mm fans became common.

Syonyk

  • Magnum Stache
  • ******
  • Posts: 4610
    • Syonyk's Project Blog
Re: I have built a whole house fan!
« Reply #7 on: March 30, 2015, 11:03:10 PM »
I'm familiar with 7v, though my current PSU is +12v only with no +5v rail.

Those old Deltas were something, though!

Syonyk

  • Magnum Stache
  • ******
  • Posts: 4610
    • Syonyk's Project Blog
Re: I have built a whole house fan!
« Reply #8 on: May 06, 2015, 04:17:05 PM »
Build blog with links to parts:

http://syonyk.blogspot.com/2015/05/house-fan-for-vertical-windows-diy.html

A month and change in, it's working exactly as I hoped.  It sucks a serious amount of air through the house, is loud but not unreasonably so, and has some serious static pressure to deal with pushing out against the wind.

The cost is certainly on the high side for what it is, but I do genuinely expect it to last nearly forever, and I can run it off solar and batteries if I'm using it to vent a shed or something in the future.  I'm very happy with the results.

zolotiyeruki

  • Walrus Stache
  • *******
  • Posts: 5603
  • Location: State: Denial
Re: I have built a whole house fan!
« Reply #9 on: May 07, 2015, 07:33:36 AM »
Out of curiosity, does the wind consistently blow from one direction?  Why not orient the fans so they blow in the same direction as the wind?

Bob W

  • Magnum Stache
  • ******
  • Posts: 2942
  • Age: 65
  • Location: Missouri
  • Live on minimum wage, earn on maximum
Re: I have built a whole house fan!
« Reply #10 on: May 07, 2015, 07:51:06 AM »
Nice trick!   

If you're trying to get by without AC I would suggest a nice $40 fan blowing directly on you in bed at night.   The whole house fans are nice for drawing in cold air at night but they will provide little direct cooling.   Kinda depends on your area and situation I suppose.   

We spent at least 1 summer with no AC and 6 weeks of very humid 100+ days and nights at 85ish.   We slept in the lower rooms with a fan on each of us.   It worked pretty good. 

We were thermally adapted though. 

zolotiyeruki

  • Walrus Stache
  • *******
  • Posts: 5603
  • Location: State: Denial
Re: I have built a whole house fan!
« Reply #11 on: May 07, 2015, 09:09:05 AM »
This week's dramatic temperature increases have reminded me that I need to finish that whole house fan project I started last year...

Syonyk

  • Magnum Stache
  • ******
  • Posts: 4610
    • Syonyk's Project Blog
Re: I have built a whole house fan!
« Reply #12 on: May 07, 2015, 09:43:45 AM »
Out of curiosity, does the wind consistently blow from one direction?  Why not orient the fans so they blow in the same direction as the wind?

The wind is fairly consistent, and mostly useless for this case - it blows from the south, so if I have all the windows open, I manage to take hot air from the southwest facing office and blow it through the rest of the upstairs.  It doesn't resolve the 10-15 degree difference between upstairs and downstairs, and my furnace is not so equipped to just run the blower without heating (whoever built the house didn't want to run the extra wire to do it, and as I rent, I don't exactly have permission to rewire the furnace).

The peak heat load is in the late afternoon, simply based on the exposure, and the wind starts dying down then as well, so the past few years, it just gets terribly hot in the afternoon/evening and a combination of wind and box fans doesn't do much to solve this.

The change that prompted this build is that this year, we have a baby, so the ferrets (which don't deal well with extremely high temperatures) are in the office, and the baby's room is upstairs (it used to be the ferret room).  Blowing hot air through the upstairs and exhausting through the baby's room isn't an ideal way to keep a baby happy, and if the office temperature gets to where it did the past few summers, I'll either have the ferrets spending a lot of time downstairs where it's cooler, or I'll have some dead ferrets on my hands.

These fans have enough power/static pressure to draw the cool air up from downstairs and exhaust it, so I can make use of the "cold sink" down there and the shaded windows with cool intake air.  In theory.

If you're trying to get by without AC I would suggest a nice $40 fan blowing directly on you in bed at night.   The whole house fans are nice for drawing in cold air at night but they will provide little direct cooling.   Kinda depends on your area and situation I suppose.

We were thermally adapted though.

We use a box fan at night to keep us cool at night, and just sleep downstairs if it's too hot.  But see above about ferrets and baby.

This moves enough air that I should be able to keep things a whole lot more livable this summer.  And, when I move, they're perfectly suited to vent a shed or shipping container or such with solar, a 12v battery, and a timer.

Also, I rent, so a whole house fan or similar is not an option.  This is the best I could come up with for my place.
« Last Edit: May 07, 2015, 12:12:35 PM by Syonyk »

guitar_stitch

  • Bristles
  • ***
  • Posts: 280
  • Age: 39
  • Location: Jacksonville, Florida
Re: I have built a whole house fan!
« Reply #13 on: May 20, 2015, 01:16:58 PM »
It's creative, for sure.  I think the noise factor may be an issue for me.  I would be more inclined to go with an inline duct fan.

Syonyk

  • Magnum Stache
  • ******
  • Posts: 4610
    • Syonyk's Project Blog
Re: I have built a whole house fan!
« Reply #14 on: May 20, 2015, 01:22:22 PM »
I considered duct fans, but the space they take is significantly greater on my desk.  This literally fits in the window with no extra space taken.

The noise is present, but not terrible.  I'll unplug it if I'm annoyed by it sitting at my desk, but it runs most of the time.

Guses

  • Pencil Stache
  • ****
  • Posts: 915
Re: I have built a whole house fan!
« Reply #15 on: May 20, 2015, 01:54:49 PM »
I did something similar for a fireplace insert fan except I already had all the parts on hand so the cost was 0$. Also I added zalman fan controllers to modulate their speed (which you can probably do with your setup too).

How come it cost so much? I am thinking that you can salvage most of these parts for free or nearly free.

Since you are using deltas, I am assuming you don't really care about noise either...

Syonyk

  • Magnum Stache
  • ******
  • Posts: 4610
    • Syonyk's Project Blog
Re: I have built a whole house fan!
« Reply #16 on: May 20, 2015, 02:35:18 PM »
How come it cost so much? I am thinking that you can salvage most of these parts for free or nearly free.

Since you are using deltas, I am assuming you don't really care about noise either...

Check the blog post (I added it to the original post) - it goes into some of this.

The short answer is, "Salvaged 120mm fans are generally very low static pressure fans and can't fight any moderate wind."  I already knew a box fan wasn't very useful (it couldn't move a meaningful volume of air out), so I needed something that would force plenty of air against the ambient winds.  Also, I don't like sleeve bearings, and I wanted to build something that would last pretty much forever.

The Deltas I'm using are not "screamers" - they're ~46db/ea.  Loud, but not unreasonably so.  There are some much louder Delta fans in 120mm that I opted against due to their noise.

Guses

  • Pencil Stache
  • ****
  • Posts: 915
Re: I have built a whole house fan!
« Reply #17 on: May 20, 2015, 03:05:51 PM »
I checked the blog for additional details. You should probably mention that 75$ of the 200$ was for double sided tape. :)

If you exclude that which you did not use, you are probably closer to 140$ which is a bit better.




Syonyk

  • Magnum Stache
  • ******
  • Posts: 4610
    • Syonyk's Project Blog
Re: I have built a whole house fan!
« Reply #18 on: May 20, 2015, 03:07:49 PM »
No, the build cost factors that in.

$120 in fans, $18 in fan guards, $20 in L brackets, $30 power adapter, about $15 of double sided tape.  It's about $200 as-built, with raw parts cost (including excess) being closer to $260.

Guses

  • Pencil Stache
  • ****
  • Posts: 915
Re: I have built a whole house fan!
« Reply #19 on: May 20, 2015, 03:24:49 PM »
No, the build cost factors that in.

$120 in fans, $18 in fan guards, $20 in L brackets, $30 power adapter, about $15 of double sided tape.  It's about $200 as-built, with raw parts cost (including excess) being closer to $260.

Oh... How much does it draw compared to a "real" house fan?

Syonyk

  • Magnum Stache
  • ******
  • Posts: 4610
    • Syonyk's Project Blog
Re: I have built a whole house fan!
« Reply #20 on: May 20, 2015, 03:32:02 PM »
Oh... How much does it draw compared to a "real" house fan?

It depends on the whole house fan, but "a whole lot less."

Most of them pull 5000-10000 CFM with a 24 or 36" fan.

I move around 700CFM in free air, so somewhat significantly less than a standard whole house fan.

However, as I'm renting, I can't install a whole house fan.

This is a whole lot better than not having forced air exhausting, which is what I've done the past few summers (trying to deal with box fans and inefficiently shoving air around), and the upstairs (especially the office) spends several weeks each summer being too hot for humans and ferrets.  As we have a newborn baby, I wanted to improve the situation.

Guses

  • Pencil Stache
  • ****
  • Posts: 915
Re: I have built a whole house fan!
« Reply #21 on: May 20, 2015, 03:35:49 PM »
Oh... How much does it draw compared to a "real" house fan?

It depends on the whole house fan, but "a whole lot less."

Most of them pull 5000-10000 CFM with a 24 or 36" fan.

I move around 700CFM in free air, so somewhat significantly less than a standard whole house fan.

However, as I'm renting, I can't install a whole house fan.

This is a whole lot better than not having forced air exhausting, which is what I've done the past few summers (trying to deal with box fans and inefficiently shoving air around), and the upstairs (especially the office) spends several weeks each summer being too hot for humans and ferrets.  As we have a newborn baby, I wanted to improve the situation.

So you are probably saving a bunch of kWs of electricity by using your fan over a whole house solution ( if we ignore that you cant install one anyway).

I run my kitchen fan on medium speed (+/- 200 CFM) and my bathroom exhaust fan (+/- 100 CFM) when I want to exchange the hot air. My GF thinks I am crazy when I do that....

Syonyk

  • Magnum Stache
  • ******
  • Posts: 4610
    • Syonyk's Project Blog
Re: I have built a whole house fan!
« Reply #22 on: May 20, 2015, 04:26:58 PM »
Yes, but probably not by that much.

My system is drawing around 50-60W.

A big whole house fan will have a 1/2hp motor drawing ~375W.  Neither are very expensive to run, but the large unit moves 15x as much air.  Air movement scales quite non-linearly with fan size.

Both are radically more efficient than refrigerated air units, if you can make things work with them.  And, as I have no whole house AC, this seemed better than just letting the upstairs cook again.

Syonyk

  • Magnum Stache
  • ******
  • Posts: 4610
    • Syonyk's Project Blog
Re: I have built a whole house fan!
« Reply #23 on: December 26, 2015, 07:21:18 PM »
So, end of summer (and then some) update:

This worked brilliantly.

http://syonyk.blogspot.com/2015/12/a-post-summer-review-of-my-vent-fans.html contains the full review, but in a nutshell:

- Fans, hooked to a light timer, running from about 3PM to 7AM.  The upstairs started getting hot around 3PM, and it remained cool until 7AM or so when I turned them off.
- Inlet filter, duct taped in a window, with a shroud to keep the rain off, worked perfectly.
- The house remained significantly cooler this summer, despite being much hotter outside, and was quite comfortable upstairs instead of being very uncomfortably hot as in previous summers.
- Power draw of ~60W, 16h/day, $0.10/kWh, 6 months: about $18 in power, all summer, for a comfortable house.  We have a window AC unit, and were able to use it *significantly* less, because we cooled the house down at night (thermal mass for the win).

Zero observed wear on the bearings, the fans are all in great shape, and will continue to be used for venting various places that need venting in the future.

If I were to do this again, I'd add a variable speed control, and perhaps bolt the fans to the angle aluminum for easier replacement, but I don't think that's likely to be a problem for the next 5 years at least.