Using attic heat to warm up basement

[Xringer]

I just scanned the exhaust vent and it's warmer than I've ever seen it.
The attic temp was 74.4F and 73.5 air is coming downstairs!
Earlier measurements at the exhaust vent were always just a few degrees
higher than the basement temp.. I need more Plastic shopping bags!!

[Xringer]

This is the data taken this afternoon, right after blocking up the ridge vent with shopping bags.
Starting at 13:30, I took many IR scanner readings on the attic exhaust vent (as in pic above),
and they were all about one degree F lower than the peak temperature.
For the first time, we could actually feel some real usable heat coming out of the vent.

The warm air output stayed steady right up to shut down at 66F.
After the fans turned off, the attic plot line stayed on the same track.
Almost like the fans hadn't been dropping the attic air temp at all.

For about 4 hours, the blowers were moving about 200cfm of warm air into the basement.
Approximately 48,000 cubic feet of warm air!

As you can see from the plot lines, it wasn't too warm today, but the sky was mostly clear.

I just looked at the weather. Next few days are going to be awful..

[Xringer]

I think the reason the basement air temperature is changing very little,
is likely due to the coldness of the floor slab. It's about 57deg F everywhere in the basement.
I think it's sucking up the heat like a sponge..

I've been thinking about sticking a sensor in the slab, so I can monitor it's heat.
I'm a little surprised to see the slab so cold, this early in the winter season.
Temperatures this month have been pretty normal.
Nothing that would cause the slab to be extra chilly..



It was 46F on the slab last winter.. (‎February ‎05, ‎2013)
Cold Basement Video by Xringer | Photobucket

That seems a little too cold, and it's got me wondering how much the slab
warmed up over the summer? All summer, it was 65~70F in the basement.

Maybe the ground around the house and under the slab didn't fully recover from last winter?
Back in the good old days, the slab was warmer.. Maybe around 65F this time of year..


I'm thinking about something very weird right now..
The possibility of using this attic air heating system,
to heat my basement during the Summer of 2014..

If we had enough low humidity days, I could run the blowers and easily
heat the basement air to 72~75F, on the summer days..
Unless the slab has ice under it next summer!

[MN Renovator]

"I'm thinking about something very weird right now..
The possibility of using this attic air heating system,
to heat my basement during the Summer of 2014.."

Don't do that. You'll be heating the rest of the house too and need additional cooling as well as bringing high dew point air into a place with cold surface temperatures which will cause condensation and that moisture will migrate upstairs.

"..right after blocking up the ridge vent with shopping bags."
You shouldn't do this either, this will become especially important when snow starts to fall, you'll have ice dam city on your roof. Even without the issue of ice dams, attic ventilation is important for moisture mitigation and by keeping the air stagnant in the attic you are increasing your risk for mold and wood rot up there.

We ventilate attics for a reason.

[Xringer]

I would only heat the basement on "low humidity days" per above.
My RH sensor tells the CAI when it's okay to run the blowers.

I'm not worried about too much heat from the basement over-heating
the living area, since we never cool the house below about 74F anyways.
The 'heating' temp of the basement could be set to match the temp of the living area.


The ridge vent is new. The roofer sawed a ragged slot down the peak and put on the vent cap..
I didn't really want it, but somehow ended up with it anyways. Jacked up the cost? Yeah!

Since this house doesn't have any ventilation soffits under the gutters,
(Except on the den, a new addition) we are used to getting ice dams
when the conditions are there. Snow and rain, followed by rain or melting
followed by low temps.
We have heating wires installed on the north side roof, where the sun is blocked
during winter's low sun angles.

[Exeric]

Xringer, if the attic wasn't too wet before the ridge vent was installed then the side vents must have been sufficient. I wouldn't worry too much about that. But I would agree with MN that heating the basement in summer might not be the thing to do.

Have you considered insulating the basement? You probably don't want to do that but it's probably the most efficient way to fix the problem.

[Xringer]

We store Christmas stuff, luggage and other stuff up there and never had any problem with dampness.
Now that we are getting old, I'll have to clean all that stuff out, while I'm still able.
The basement is where we have all the dampness.

In the summer, I'll try leaving the ventilation system in heating mode,
so both warm (above 66F) & hot (dry) air is pumped into the basement.

That will keep the air moving in both the attic and the basement.
Using the CAI program, I can limit how warm the basement gets,
just by shutting off the attic's blower. Or both blowers.

It if starts up at 66F in the mornings, a good bit of air can be moved
before the attic heats up to the 100F plus range.
In the summer, I think it would be nice to have the basement in the mid 70s.

If the system tries to pump down 120F air, I can just pull out the shopping bags,
to start pulling in a mixture of hot and outdoor air..

[Xringer]

It was rainy, windy and overcast all day. But there was a short burst of dim sunshine. Didn't last long.



The orange plot (DHW) can be seen going up, all the time the A7 was running.
The blue trace (basement) does the invert of the water temp..
The A7 really chills that part of that basement..
Once the A7 shuts off, you can see the warm air starts heating up the basment
fairly fast..

At "A little sun", the water temp climbed because of PV heating..
The sun was so weak, I never expected to see a 'bump'..

Edit:
As far as I can tell, the RH sensor is reading 10 to 12% higher than the 'real' RH.
I'm not 100% sure, but when I compare my RH with the local Underground Weather and the accuweather.com site,
my RH sensor reads 10 to12% too high during very damp weather.

So, in order to get a RH setpoint of 70%, I have to use 80% as my setpoint.

[Xringer]

My wife ran the dryer twice today. I can see the jump in RH and outdoor temp.
We took a bike ride to Bedford, and after we got back she did the second wash.
The drop in hot water temp on wash number #2 proceeds the RH spike from the dryer exhaust.

When we returned from our bike ride, the attic temp was almost 90F.
The basement stairs was a very warm 89.9 on the IR scanner.

Basement temp readings seem to be affected by the dryer.
I noticed the basement temps jumped with the humid air blast from the dryer.
The door of the dryer scanned at 90F.. That door is only 8 feet from the sensor.

Lesson learned:
Don't install sensors close to heat (or humid) sources.



It was a pretty mild day, but we had good solar. Best 'heating' of the basement so far.

[jeff5may]

Looks like you could stand to run some of that hot attic air straight into the airtap. It would definitely boost the cop of the unit, while offsetting some of the cooling of basement air. Literally moving the hot attic air into your water heater at high efficiency. Maybe a couple of lines in the plc code to run some warmish, more humid air towards the unit for more latent/less sensible heat removal? Hot, humid attic air turns to cold condensate down the drain rather than cold, dry basement air...