Exhausting air from vaulted ceiling with no attic or insulation

Reply

  #1  
Old 08-07-18, 10:00 PM
F
Member
Thread Starter
Join Date: Aug 2017
Location: usa
Posts: 18
Received 0 Votes on 0 Posts
Exhausting air from vaulted ceiling with no attic or insulation

Hi. We bought this house in December and put off getting mini splits until we could see what the different parts of the house would be like in summer (mini splits because central air couldn't make it to all the weird additions in the house, though also b/c mini splits are cheaper and more efficient--the gas service is cut off because of a punctured gas line, so no real heat [see the last paragraph for an explanation of why this isn't a huge concern]). Well, it was a good decision, because we now understand the impossible hot spots. One is an addition above a now-converted garage. The addition has 15' high (I guess) vaulted ceilings with exposed beams and apparently nothing (no insulation, no air space) between the roof decking and the wood planks that constitute the visible ceiling between the beams (I've surmised this by measurements finding 1 1/2" between the shingles and the visible portion of those boards). It's just shingles/plywood/nicely finished planks. There are no vents in or out, so no air moves up there. So, it's very hot in the room during the day, and the ceiling itself is hot (measured well over 100 degrees with an infrared thermometer recently on a day with a high temperature of 88).
Here are some photos of the room:
One
Two
We need to find a way to cool this room without seriously taxing our mini split system, which will come soon or even turning it on on mild days. One major catch is that this is also a cold room in the winter due to the stupid high ceilings and no insulation. We thought very hard about constructing a ceiling and making a properly insulated and ventilated attic, but that's a huge job requiring lots of very long beams across the room (which is something like 18'x18' but also has an attached bathroom and closet and hallway that are all part of the vaulted envelope (not sure I'm using that term right). So, I want to add some way to exhaust this hot air and even cool off the surface of the ceiling by moving some air up there. A whole house fan is not the right choice because those are made to blow into a vented attic, so we'd have to rig up a vent on top of it on the roof, which might be difficult. An attic fan would be a more reasonable choice since those come with attached vents. However, the problem with both options, and any other exhausting fan (another idea addressed below), is that they will have no way of stopping warm air from escaping in the winter, making the room even harder to heat. I've been looking at through-wall and through-ceiling fans like these, some of which (wall-mounted units) can move around 500 CFM, which might be okay mounted at the highest point in the wall, but it seems that these have the same problem as roof or attic fans: they'll let out warm air in the winter. One option would be exhaust fans that have shutters, like these, The only drawback is that I've read that those shutters don't actually do a good job of keeping warm air in the way one would hope.
So, my best idea so far is a venting skylight paired with a ceiling fan to suck air upward and eventually out the opening (the room will have open windows to draw air in and up and out, air which will be cooler than that high ceiling air further heated by that radiating roof regardless of the temperature outside). This would be able to close tightly in the winter to prevent (much) warm air from escaping. There are two drawbacks to this idea: 1) a skylight lets in even more heat-producing sunlight (though we could mount it on the east-facing roof and not get much direct light through it) and 2) it's expensive. I might also add that I'm a little nervous about cutting such a large hole in the roof when I don't really know what I'm doing. There's plenty of space between the beams, but--really--what else is up there? I don't know for sure.
Soooooooo, anyone have any advice here? The internets are full of people talking about ventilating vaulted ceilings that have some drywall and airspace above them, but I've literally been researching this problem for weeks and have never seen anyone with this precise problem. I did see one person recommend a louvred wall vent made by Tamarack Technologies, but I don't actually see it on their products list, and it was reportedly quite expensive, nor do I know how well the louvres hold in warm air in the winter.
Oh, uh. I should mention that I live in San Diego. Now, you're all like, "this jerk is complaining about hot and cold in San Diego!" I know, I know. I've lived in New York without using a heater, and I lived here in apartments for years without heat or air, but now I've got family living with me, including some vulnerable members who need some comfortable living spaces, and some of our rooms have hit nearly 100 degrees this year. The room in question will be for an adult with cognitive disabilities who is not good at self-regulating behavior to adapt to weather (wants to wear his sweaters on hot days) Soooo, what do you say? Any bright ideas? I hope I've given ample info for those of you with knowledge and a minute to think about this.
Thanks.
Mike
 

Last edited by PJmax; 08-07-18 at 10:34 PM. Reason: title corrected
  #2  
Old 08-08-18, 06:24 AM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 24,425
Received 747 Votes on 686 Posts
Do you have a short version of your question?
 
  #3  
Old 08-08-18, 07:09 AM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 10,524
Received 37 Votes on 34 Posts
Ditto on the short version, I like to help on ventilation issues but I hate long posts. I'll be back for the pilot (short version) .

Bud
 
  #4  
Old 08-08-18, 08:19 AM
F
Member
Thread Starter
Join Date: Aug 2017
Location: usa
Posts: 18
Received 0 Votes on 0 Posts
Sorry. The short version:
How does one exhaust hot air in summer from a room with a high, peaked ceiling with no attic or insulation without also making the room even harder to heat in the winter?
Most products (1, 2, 3, 4) are designed to vent air into an attic or out of an attic and aren't good at sealing when the fan is not in use. Venting skylights are great but very expensive (I need an electric one).
Thanks.
Mike
 
  #5  
Old 08-08-18, 08:46 AM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 10,524
Received 37 Votes on 34 Posts
Hi Mike, much better.
I saw San Diego so on the hot side. But hot or cold climate all ceilings need insulation. I'll add a related link but my first thought would be a sealed unvented approach, but more details would be needed.
http://www.greenbuildingadvisor.com/...hedral-ceiling

Bud
 
  #6  
Old 08-08-18, 09:20 AM
Andrew's Avatar
Member
Join Date: Apr 2003
Location: USA
Posts: 1,017
Received 14 Votes on 10 Posts
You will want to go with a roof mounted fan, similar to those used in commercial buildings. A roof curb with a backdraft damper would be installed on the slanted roof, then the fan mounts on top. See the link for an example of the fan style I'm referring to:

http://www.greenheck.com/media/pdf/c...GB_catalog.pdf

Andy
 
  #7  
Old 09-20-18, 10:06 PM
N
Member
Join Date: Sep 2018
Posts: 1
Received 0 Votes on 0 Posts
Vaulted ceilings in only half of mobile home and fan in half attic.

Hello,
I'm not sure if anyone can help me here... or if I'm in the right place to ask for help with a question...
we bought a mobile home with a fan in back end of attic. The fan started coming on automatically when the weather cooled outside... it seems.
Should we leave the fan turned on in the fall? In other words, does the air in attic need to be vented?
 

Last edited by NeedAnswers2; 09-20-18 at 10:08 PM. Reason: To make clear my question
  #8  
Old 09-21-18, 12:05 AM
steve_gro's Avatar
Member
Join Date: Jan 2004
Location: San Francisco
Posts: 1,092
Received 1 Vote on 1 Post
In a similar situation to the first poster, a ceiling fan was very helpful.
 
  #9  
Old 09-21-18, 09:37 AM
2
Member
Join Date: Jan 2014
Location: USA near Boston, MA
Posts: 985
Received 69 Votes on 59 Posts
While I agree that insulation and ventilation are key ingredients of heating and cooling a room, do not overlook the fact that warm air rises and cool air sinks. If you don't move the air around (like with a ceiling fan or a ventilator) it will stratify and you may be able to cool the lower part of the room to a comfortable temperature in spite of the high temps at the top. (Obviously, heating is the opposite. But your heating needs are not so extreme and may not be as big an issue.) Depends also on the height of your ceiling. I imagine it will be difficult, however, to determine what size unit you will need since most calculations deal with the entire volume of the space being heated or cooled.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: