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Old 10-19-13, 04:18 PM   #1
Xringer
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Default Using attic heat to warm up basement

The goal of this project it to pump solar warmed air from the attic, down to the unheated basement.
For two reasons:
I want to be able to work in the basement when during the winter.
(When it's 60-65F down there).
And, I want to provide a little warm air for the A7 Airtap (DHW ASHP).

I have an exhaust blower already installed in the basement.
The air intake is 10" off the basement floor. It's suppose to pump the cold air into the outdoors.



My CAI controller is using temperature and RH as inputs and X10 for control.
I've had success in using this fan during this summer, pumping out
the cool damp air, while the outdoors RH and temp are within acceptable ranges.



This new 200 cfm fan (coming next week) will be installed in the attic.
It will also be controlled by X10.

4" inch 200 CFM Inline Fan Duct Booster Exhaust Vent Blower Hydroponic Radon M 4 | eBay

I plan to use this 4" dryer duct hardware for the attic install.

The tubes are 8' x 4" and should fit the Tjernlund M4 blower.


The dryer exhaust port will be mounted on the ceiling of the small back hall
(or landing) that connects the basement stairs to the kitchen and back entry door.
This 'hall' is where the pull-down attic stairs is located, so the install shouldn't be too hard.

Using the outdoor RH reading and attic temperature (and time of day),
the CAI controller will turn on both blowers when the RH is low
and the sun has heated up the attic.
I'll post the control program after I get it debugged.

I've been thinking of a method of closing the plastic flap inside the dryer exhaust port.
It would be nice to keep warm air from floating up into the attic during the night.
Some fishing line with one end weighted, thru the flap, connected to a hook on a roof rafter.
The light weight will pull the flap up, and it will be easy for the air flow to push down (open).

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Last edited by Xringer; 10-19-13 at 04:27 PM..
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Old 10-20-13, 03:24 PM   #2
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Default Dusty part done

Here's a "Before" picture of the back door and pull-down attic stairs.




Here's the "After" pic with the dryer vent installed.

(Notice the roof rafter? I left the attic light on)


Because it's one inch of sheet-rock, I used long deck screws and used PVC plates
on the top side, to act as 'nuts' to hold the vent from being shaken loose
by vibration from the blower.

The hole saw used, was 4.125", but the fit was too tight. I had to sand down the ID of the hole..
Amazon.com: MK Morse AV66 Hole Saw, 4-1/8-Inch Bi-Metal Boxed: Home Improvement
I used a dust mask! And went out on the deck to shake off.. Looked like a ghost..

Not real sure about the wisdom of using this directional vent.
It's nice that it will point the air flow in the right direction (downstairs),
but I fear it's going to generate a good bit of noise..
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Old 10-20-13, 03:35 PM   #3
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Default

Cool stuff. Have you monitored attic temps in the winter? I haven't done it religiously, but I do know it won't get up to 60F in winter. Its pretty well ventilated though.
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Old 10-21-13, 11:14 AM   #4
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Quote:
Originally Posted by Daox View Post
Cool stuff. Have you monitored attic temps in the winter? I haven't done it religiously, but I do know it won't get up to 60F in winter. Its pretty well ventilated though.
I'll have to go back and look at some of my postings.. But I think the 70s
might be pretty common during the mild parts of the winter.

It got down into the 30s last night, so it took a while to warm up this morning.


(I love these charts and need to make my own from the CAI data)!

Right now, at 11AM. ----------- At 14:42
61.8 F in the basement----------62.7
58.4 F outdoors -----------------63.4
70.7 F in the attic Peak----------95.1

I had the blower set to come on at 65 F(in attic), and it came on around 10AM.

Not doing much good now, but when I get all the attic hardware installed,
it will be sucking down that warm peak air..

My plan is to program a differential function into the CAI board.
If the RH and time of day are good, it will pump warm air down from
the attic, anytime the attic air is warmer than the basement air..

In the dead of winter, I may have to change to program, so that I can
pump down some no-so-warm air, cool down the basement a little,
pause and let the basement come back up(GeoSlab) to normal and repeat..
Hopefully, I won't have to resort to using the cold air flush..
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Last edited by Xringer; 10-21-13 at 02:43 PM.. Reason: Adding temp change at 14:42
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Old 10-21-13, 11:19 AM   #5
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Well, its still better than sucking in ambient air not matter what, which is what your fans were doing before. Even if its not-so-warm, its also not-as-cold-as-outside.
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Old 10-21-13, 05:17 PM   #6
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Default data logger

I joined an interesting forum a while back.. Today I looked for a CAI data logger and found one!

CAI WebControl Logger [Software] - Page 11 - CAI WebControl - CocoonTech.com

The download link is Weatherbyrifler - Downloads Area - Exe Filer - CAI WebControl Logger v1.4.7

I'll be checking this out, to see how it works with OpenOffice..

So far, it looks very interesting..
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Old 10-24-13, 08:35 PM   #7
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Default Attic blower installed

Today I took data, while I waited for the UPS guy.. (He came at 5:41 P.M.)
The attic temp got into the high 70s, since it was pretty cloudy today..
Outdoors stayed in the low 50s all day.. The basement stayed pretty stable.




After supper, I installed the new fan and dryer duct in the attic..
Dang thing sounds like a jet engine! But, it's not too loud when the doors and pull-down stairs are closed.


I put a filter 'sock' over the warm air in-take. Hope it stops some of the larger particles.

The forecast for tomorrow is cooler, but mostly sunny..
I'll try to get the data logger running before the attic heats up,
and see how well this rig is going to work on a mild day..
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Old 10-25-13, 07:28 PM   #8
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Default Solar? Too many clouds!

The forecast didn't work out.. Maybe tomorrow we can get some real sun..

Pretty cool and cloudy for most of the day. The PV heated water tank climbed in unison with the attic.
But, it didn't cool off as fast. Again, the basement temp was pretty flat.
I was able to tweak the program a bit and got the fans turning off & on nicely.
I used a setpoint with only a 3 deg differential (warmer in the attic)
and tried a 5 deg diff later in the afternoon. I can see that a higher
number is going to be needed.. Maybe 8 or 10 degs F.
Air that is just slightly warmer than the basement has very little impact.
I could feel very little warmth down there. Barely noticeable.

I can't wait to see 80s or 90s in the attic. That's going to warm up the basement stairs, at least.



Notes:
I did some measurements of the slab.. It's pretty uniformly cold <60F.
Warming up the air in the basement looks like an uphill battle..

I've had the A7 unplugged, for a few days, and with little sun to heat the
water tank, it's been dropping a lot. But, it's a good indicator of sunshine.

One thing surprised me. Even when the sun was dim, sucking the air
out of the attic, didn't really drop the temperature up there very much..
I had expected to see a pretty rapid drop in air temp (in the peak area)
when the blower started moving 200cfm downstairs..

But, that wasn't the case. The temp drop was pretty slow.
I think the main reason it dropped below the set-point,
was due to the lack of solar..

Yesterday, early in the morning, when the sun first hits the roof, I was out there with my IR scanner.
I measured 85F on the singles. But, when I went inside and scanned the
attic boards near the peak, they were only in the 50s..
This lag-time (plus the observation above) leads me to think
my roof is a pretty good thermal mass.


~~~~~~~Edit 9:43 AM
It's sunny now, but it looks like a ton of clouds are rolling in..
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Last edited by Xringer; 10-26-13 at 09:44 AM.. Reason: Weather report
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Old 10-26-13, 12:11 PM   #9
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Default

Quote:
Originally Posted by Xringer View Post
One thing surprised me. Even when the sun was dim, sucking the air
out of the attic, didn't really drop the temperature up there very much..
I had expected to see a pretty rapid drop in air temp (in the peak area)
when the blower started moving 200cfm downstairs..

But, that wasn't the case. The temp drop was pretty slow.
I think the main reason it dropped below the set-point,
was due to the lack of solar..
Yep, I've found this to be the case too. This is why I've recommended and plan on adding additional fans to harvest more heat. I've had my fans going after 10pm sometimes...
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Old 10-26-13, 03:07 PM   #10
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The good thing about using attic heat to warm up the basement is that you can use cooler air than for heating the house, so there are more days during the year when you can harvest this lower grade heat. And a warmer basement = warmer floor above it.

Xringer, iirc you mentioned that you pump warm air from the attic into the basement, and at the same time pump cooler air from from the basement floor outdoors. Why not pump the basement air back into the attic, since it is (most likely) warmer than the outdoor air that is being sucked into the attic?
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