Removing Hot Air from Vaulted Ceiling

[Todd]

Hi,

I have a two story house with vaulted ceilings throughout. I had AC put in last year, but the upstairs doesn't really cool down. The front of the house has the biggest windows, and is West Facing, so it gets all of the afternoon sun. Last year, I also replaced all of these windows with much more efficient windows.

However, I can't get it below 80 degrees upstairs. And this can often be when its cooler outside.

In examining my options, I noticed that I have NO vents on my roof. I have all vaulted ceilings, so I don't have an attic. I do have some soffit venting on either side of the slope of my roof.

Can I put turbine vents on the roof? Will this make a difference in temperature for those upstairs rooms if I can cool the space between the ceiling joists and the rafters? Again I have NO ATTIC.

Really, what I'm looking for is a way of removing that hot air from the vaulted ceilings in the summer.

Any suggestions? Turbine vents appear to be an easy solution. Will cooling the space between the roof and the ceiling help in cooling the room below it?

- Thanks in advance,

Todd

[Just mee]

Ceiling fans will work well for vaulted ceiling. With a remote

[barry]

Maybe. Soffitt venting might be useful, _if_ it's of adequate inlet area _and_ air coming in there can move up inside the roof deck and escape somewhere. ,

Insulation between ceiling and roof deck could block airflow, unless spacers were installed between insulation and roof deck. You mention nothing about this.

Ridge vent could work, and is simple, elegant solution, depending on stuff mentioned above. Thermostatically-controlled fan(s) with mushroom-looking enclosure would work.

Ask locally, and/or visit big-box.

J

[Todd]

But how is it that venting the this space will help remove the heat from the ROOM below it? This is what I don't get. I understand venting the soffit, but I don't know how that will allow the heat in the room below (with the vaulted ceiling) to cool down.

Any thoughts on this?

- Thanks,

Todd

[trader4]

First you have to realize how a vaulted ceiling is constructed. Essentially you have spaces that are seperate channels, running from soffit to peak of the roof. If you put in a turbine type vent, or a simple box vent, all that is going to vent is the one channel. You'd have to put one in between every rafter to vent the whole thing.

A ridge vent is the correct solution. However, the next thing you are up against is how much insulation was put in and how it was installed. If it's too thick there may not be room for air to flow above it. If it's pushed up over the soffit vents, air can't get in. The right way for this to be done is to use plastic baffles that go in above the insulation, beneath the decking to keep the channel open. Unfortunately, you have no way of knowing how yours was done.

You don't have anything to lose by adding a ridge vent. It can't hurt and if air can flow, it will help a lot.

To answer your other question, this can help reduce your room temp because it helps decrease the temps directly above the insulation. However, if it's 80 deg, adding a ridge vent ain't likely to cure that. I'd get the ace AC guys that did the install back and see what they have to say. Did they install sufficient returns up high?

[Todd]

I don't think that my vaulted ceiling is contructed in the way that you suggest. I think that there aren't seperate channels, but rather an area in between the rafters and the ceiling joists. I don't think they are conected to each other, which would, as you suggest, create seperate channels.

I could be wr> First you have to realize how a vaulted ceiling is constructed.

[m Ransley]

Didnt you get a guarnteed temp drop from your AC installer, I bet he did not do a written load calc, he just guessed on what you needed. Do you have a second floor return, second floor AC wont work without. Call your AC guy back first. Is there an air gap that allows any venting in your roof design, you may or may not be able to do more, but it probably wont help anyway.

[trader4]

Having the roof decking on one side of the rafters and the the ceiling on the other is the simplest, cheapest and direct way of creating a vaulted ceiling and it gives maximum height. If yours is done with seperate rafters for the roof and ceiling joists with a space in between, then you could ventilate that by means other than a ridge vent, like your turbine idea. However, I still think in that case, a ridge vent is still the way to go.

[scott21230]

I'm guessing that you have a n older house made before A/C or otherwise doesn't have proper ducting for A/C. In order to get rid of the hot air, you need a return air in an area where it's hot. If your lowest return air grill in near the bottom of an upper floow (i.e. in the floor itself or low on the wall) then you will need a return air placed higher to draw in the hot air instead or recirculating the already cooled air.

[barry]

Hi, Todd.

How do you think the interior air (mostly) gets heated? Unless you didn't tell us about the forge/smelter you're running in there, I'll wager that the majority is coming from above. And you want to stop that, by diverting it harmlessly (read: avoid roasting roof.)

Thus, if you dissipate heat from roof (see my previous about ridge ventc, etc. too) it won't heat the innards. Infrared transmission can move some serious energy.

You still haven't told us anything about what's between the ceiling and the roof deck. Please investigate & report. You need to know this.

Once you control unwanted entry, then it makes sense to throw $ at reducing the rest.

J

[Todd]

The house wasn't built for A/C, it was built for heating. It does have central heating, so added A/C wasn't a big deal since all of the duct work was there. However,

a.) the ducts upstairs aren't as wide, to prevent TOO MUCH heat from getting to the upstairs during the winter

b.) the return air upstaris was located at the bottom of a wall.

I put a second return air register as high as I could go right over the existing return register, just 8 feet higher.

The problem is that the only air return occurs in the hallway, and not in my bedrooms surrounding the hallway. And the bedrooms surrounding the hallway have vaulted ceilings as well.

Its would be great if there was a way to get the hot air in the bedrooms into the hallway and down the air return.

But still, i figured that venting the space between the ceiling and the roof would better cool the room. I dunno.

- Todd

[e-mail] wrote:

[Travis Jordan]

What did the contractor's heat gain calculation say that you needed in BTU to cool the house, and how big a system did they put in? Is it zoned?

[HeyBub]

Get a ladder.

Is the ceiling significantly hotter than the air around it? If so, the heat in the air is coming from the ceiling.

If not, the heated air is coming from the rest of the house (heat rises).

Also, think trees.

[Todd]

Thats a good thought. I will check with a ladder.

I imagine that its a combo of things -> the heat rising, AND the roof collecting heat.

HeyBub wrote:

[m Ransley]

Do you have insulation in the roof, how much, that is a first concern affecting your usage winter and summer. When I had AC retrofitted I had a second floor return added, I am able to reduce 1st floor suplies and returns by 60% or more to force AC upstairs. Ive checked the temp just over my cooling coil and have little difference as a result of reduced airflow. Your set up was for heat before adding AC, heat rises, you can rebalance your system a bit to help also leaving your fan on 24x7 wil help alot. Just static venting a cathedral may not be the issue or help.

[JimL]

Exactly. A couple of points. 1. If at all possible, leave the heated air in your vaulted ceilings. No fans are anything to disturb the hot air. It is where it should stay. The temp below can be 5 degrees cooler if you don't disturb it.

1. Your house should have been built with ridge vents all over your roof. And there should a channel for the air to travel up from soffit to ridge vent. Lowe's sells them. And of course lots of insulation directly behind your cathederal ceiling. When you reroof, fix it. Or else rip out the sheetrock and fix it when you get fed up with high energy bills and hot house.
2. You definitely need two separate units until you fix the problems.

[nicksanspam]

Or an IR thermometer.

I guess we need the ladder to measure the air temp. Aim the thermometer at a piece of paper...

Nick

[JimL]

Why paper? Do you get false readings otherwise?

What should I beware of?

[Chris Hill]

I'm sure that if the sun is shining on the windows you have heat coming in through them. Put shades or tinting on the windows.

[nicksanspam]

Maybe. You can't read an air temp with an IR thermometer, because air is transparent to low-temp IR radiation. If you aim an IR thermometer at an indoor surface, you will get the temp of the indoor surface, which may be warmer or cooler than the air temp. One way around that is to aim it at a piece of paper, ideally after waving the paper in the air to ensure it's close to the air temp, even if other surfaces exchange radiant energy with the paper.

Nick