Pulling heat from attached sunspace?

Hi everyone,

I’m working on ideas for moving some of the warm air created in my 1970s-era attached sunroom/sunspace I recently renovated into my home, and I’d appreciate some feedback. I’ve attached a picture of the sunroom. The dimensions are approximately 18’ x 16’ with the south, west and north sides being all 76 x 34 clear tempered insulated glass units with ½” air space in between. The total air volume within the space is approximately 5000 cu ft and I’ve sealed it to be reasonably airtight (although there are 4 sets of patio doors, 2 up, 2 down, that certainly leak some air). The floor is poured concrete approximately 5” thick; I plan on adding a little more thermal mass with a “flooring” layer of 2.5” pavers later this Fall. There is no other thermal mass other than the shared wall with the house which is stick construction/thin layer of stucco.

The sunroom spans two stories of the home: the basement level of the home is the floor level of the sunroom and there is a standard size door between the two. And there is a balcony/walkway at the level of the main floor of the home. There are two sets of sliding glass patio doors between the main level of the house and the sunroom walkway. When we’re home, it’s easy enough to slide those patio doors open and get some heat moving into the house that way (and even get some circulation by cracking open the door between the basement level of the home and the sunroom). But obviously this arrangement only works when there is active heating and when someone is there to close things up when that heating stops. I’m wanting to install some kind of fan-driven system that would automatically move air from the sunroom into the house when the sunroom temp rose above a certain level, then shut off that air movement when the temp fell below.

The basic design I’m playing around with is running a 6” or 8” standard wall/vent pipe vertically along the wall shared by the sunroom and the home (on the sunroom side). Since the roof/ceiling of the sunroom is a simple sloped/shed design, the “intake” end of the pipe would run vertically to about 6” or so of the ceiling to capture the warmest air pooling there. The pipe would extend straight down vertically and then penetrate through the wall and into the house with a “T” or elbow. I’d install a thermostat-controlled inline fan that would blow heated sunroom air into the house above a set temp, but turn off below that temp. I would install some kind of gravity or spring-controlled damper to close the pipe when the fan was not blowing, hopefully preventing (most) air movement in or out.

Finally, I was considering the need for some kind of “return air” capability, otherwise it would seem I’d just be pulling much colder outside air into the sunroom fairly quickly once the warm air had been pulled into the house. So I was thinking of installing a short section of 6” or 8” pipe (or some kind of vent) through the wall at the basement floor level, again with a gravity or spring damper. The idea would be that when the inline fan was blowing, that would create sufficient pressure (?!) to pull that basement-level damper “open”, pulling cooler basement into the sunroom and creating a continuous “heating loop” from basement to main level.

So that’s the outline of a basic plan, but I have more than a few questions:

1. Is the overall design good, or is there another approach to consider that would accomplish the goal?
2. 6” versus 8” pipe? The 8” pipe elbow/”T” is pretty darn big and unsightly, and may be more than I need to move the air for this particular sunroom. 6” inline fans, however, seem to be limited to around 250CFM which may not be sufficient to create the pressure to open the basement-level damper/pipe.
3. Would it be better to penetrate the wall near the ceiling level of the main floor of the home, or near the floor level? I suspect the floor level might be better for air movement, but ceiling level would interfere less with furniture placement.
4. I’m not sure of the best place in the pipe to mount the fan and the damper…I was thinking the damper right near the “end” of the pipe penetrating into the main floor of the house, with the fan mounted just behind it (although people seem to have more luck with gravity-powered vertically-mounted dampers than spring-powered horizontally-mounted ones)

‘Any advice/feedback greatly appreciated!

Fans are noisy. I'd consider noise abatement as one criteria on where to site the fan. I sometimes wish that my setup had two controllers. One to power the fan if heat is available. And one to interrupt the power if the house is overheating. We partially got around this issue by putting the makeup air intake in the basement, and installing a larger fan (10" ducting) so that it tended to heat the whole house rather than just one room. We dumped the air into the ceiling of the living room. The floor would have been nicer cause we could have laid on the vent. But the ducting was ran based on what was easy/cheap and not on what was best.

Thanks for responding. I'm not sure I'm following exactly what you ended up doing, could you describe it in a little more detail? So you used 10" ducting and 10" inline fan. Did you install that fan right at your living room level or down in the basement where you makeup air/intake was? I'm wondering if you had a powerful enough fan blowing cooler basement air OUT into the sunspace, whether that would be enough to push the warmed air through the piping into that main/upper level...enough pressure to open a damper?

Joseph Lofthouse wrote:
[snip] We partially got around this issue by putting the makeup air intake in the basement, and installing a larger fan (10" ducting) so that it tended to heat the whole house rather than just one room. We dumped the air into the ceiling of the living room. The floor would have been nicer cause we could have laid on the vent. But the ducting was ran based on what was easy/cheap and not on what was best.

I'm don't know how you would implement it in your situation but the principal I use is to move cold air from the space you want heated to the heat source (to become warm air). This sets up a natural exchange of cool air for warmer air just like the cold air return in every installed heating system.
The warm air will naturally move to where you've removed the cool air.
When you blow warm air into a space it has trouble displacing the cooler, denser air.

Coyote Fred : Heres a thought project go sit in your car. pick a hot sunny day with a hot car interior and select the air conditioning!

After the car cools down you need to find the control that lets you take the already chilled air from the passenger compartment and circulate

that air past the Cooling coils in your car. this is better than taking un-chilled outside air and moving it [past your coils and then blowing that

air into the passenger compartment ! This is simply reducing the Air Conditioning load ! This example also works when it is cold outside and

we want a warm interior. What you want to create for this space is a Thermo-Syphoning air movement - to naturally pump heat from your

Sunspace during the day *

When your house is too hot simply opening a window as high in the house as possible to exhaust hot air while providing cooler outside air

from low on the north side of your house should reduce excess heat gain !

* A Few words about insulating curtains or shades for that massive glass wall. Cold air falls at night and will stream past you glass this continuously

moving air current will reduce the surface temperature of 1st your glass wall and eventually the whole room it is like the chilling effect from a

fast moving cold air front ! Insulated Curtains help keep heat in and on days you know is going to be hot keeping ( Light Colored ) Curtains closed

reduces heat build up ! Insulated curtains for your glass walls will help reduce the extremes of temperature change and reduce Both heating and

cooling !

Hope this was timely and helpful . For the Good of the Crafts ! Big AL

We have an ~70 foot long duct that pulls air out of the basement, and a 30 foot long one that returns it to the living room after being heated. The blower is on the far side of the garage from the living room.

Hi there and thanks for responding. OK I think I'm following your "thought project"...I'm just not clear how I apply that to my situation with this sunroom/sunspace. It sounds like may be on the right track with some kind of "circulating" system. I can imagine my sunspace as being kind of a larger version of this type of thermosyphon airspace heater:

http://www.builditsolar.com/Projects/SpaceHeating/solar_barn_project.htm

This design uses many vents top and bottom to create a natural thermosyphon. I want to limit the number of vents (holes!) in my walls, so I'm using a fan to accelerate the natural thermosyphon effect...or at least that is the theory!

[snip]

allen lumley wrote:Coyote Fred : Heres a thought project go sit in your car. pick a hot sunny day with a hot car interior and select the air conditioning!

After the car cools down you need to find the control that lets you take the already chilled air from the passenger compartment and circulate

that air past the Cooling coils in your car. this is better than taking un-chilled outside air and moving it [past your coils and then blowing that

air into the passenger compartment ! This is simply reducing the Air Conditioning load ! This example also works when it is cold outside and

we want a warm interior. What you want to create for this space is a Thermo-Syphoning air movement - to naturally pump heat from your

Sunspace during the day *

allen lumley: I'm SO sorry, I accidentally downvoted your long post about thermosiphoning... first time I ever tried to upvote something on this site and I failed
As far as the thread: I'm building a house and designing thermal mass warmed by passive solar, hooked into masonry heater (more like rocket stove) hooked into the house heat pump (heat AND cool system)... I can't be the only person who has ever done this, I assume there's a word I don't know (like Trombe Wall is a specific word, that you can look up and get a lot of info on it) if anyone has a word for this, I'd LOVE to know it... "Multi-input thermal mass wall system?"
And I have planned in: serious insulated shutters and shade drapes, 3 section windows that open top and bottom with solid pane in the middle, bare wall cover basic air heat space if I need it (don't know the word for that either) (glazed heat accumulator that can pull in and out the windows)
I'm going into the midwest from the desert, so I look at things weird. All of my previous designs were for passive cooling, trying to keep that stuff in while adding the heat.
Still learning LOTS! Thank you all for cool threads to read

Pearl Sutton wrote:allen lumley: I'm SO sorry, I accidentally downvoted your long post about thermosiphoning... first time I ever tried to upvote something on this site and I failed

Pearl, it's ok. If you click the thumb icon once, it gives a thumbs up. If you click it again, it removes the thumbs up. It won't actually 'downvote', the worst it can do is to remove an upvote you've already given.