# Gap around vent to attic.  Aft bedroom always hot.



## Toddxx77 (Jul 26, 2017)

Hey everyone I am a new first time home owner and I have 2 questions about my AC in my house. I'm sure over the years I will have many more questions lol. 
1. In my hall closet is the ac/ heating unit. There is a metal duct going up to the roof to a vent. There is a 6 inch or more gap around the duct ( square) see picture. I can see into the attic. Should that gap be filled so that air isn't going into the attic? I found this gap because rats where coming down that gap into the closet so I want to close it up. Maybe with a roll of fiberglass around it? Is it supposed to have that gap?

2. My house is shaped like a U. The last bedroom is my son's room and if he closes his door at night it gets supper hot in side. It has a gap at the bottom of the door for the return and there is decent airflow coming out of the vent. And it's cold air. But I can't figure out why it's having a hard time staying cool at night. I used a laser temp gauge to check the air coming out and it's the same as the other vents in the house. And the walls and ceiling is about the same temp too. I'm thinking I either need more air pressure in the room, or more return out of the room. Any thoughts? Maybe a duct fan or register fan?  Any thoughts would be appreciated!!


----------



## Snoonyb (Jul 26, 2017)

Welome to the site.

The opening around the pipe is for 2 reasons, 1. is fire protection, and the second may be because it acts as the required upper combustion air.

Closed HVAC systems are not allowed to use conditioned air, as combustion air and draw that combustion air from outside the conditioned air envelope.

You can and it should have been done by the installer, surround that exhaust vent with hardware cloth which will prevent the vermin intrusion, however you'll need to address the entry point to the attic.


----------



## Snoonyb (Jul 26, 2017)

Regarding the heat build up. Are the windows single glazed and covered with heavy curtains? Is the bedroom on the southwest side of the building? What is the exterior material?


----------



## nealtw (Jul 26, 2017)

That is B vent chimney B vent chimney is double walled and can be I inch away from wood the pipe rite at the furnace is single wall and it needs to be 6" away from wood.
The hole in the sealing is made for single pipe which would never happen today. Either way there should not be an open hole like this between the house and attic it should have a sheet mettal sheet with a hole for the vent.
As noted the furnace may need fire air that would be brought into the house by a duct thru the basement or crawlspace.
But as it is, it is fire safety issue as well as you are loosing moist house air into the attic and that is not what you want happening..


----------



## Toddxx77 (Jul 26, 2017)

Yes it is on the south west side, no curtains just blinds, the window faces south and the room and windows is shade by a tree on the south side. Outer wall facing west is brick. But I have checked the temp on the walls and the temp is the same as the other rooms.


----------



## nealtw (Jul 26, 2017)

See figure #1 fire stopping
http://www.texasinspector.com/files/Duravent-Type-B-Installation-Instrcutions.pdf


----------



## Toddxx77 (Jul 26, 2017)

So I should make a metal square cover with a hole in the middle for the duct to go through to patch that hole?


----------



## nealtw (Jul 26, 2017)

Toddxx77 said:


> So I should make a metal square cover with a hole in the middle for the duct to go through to patch that hole?



I have not done enough to know what pitfalls you could run into. The furance guys would have the sheet with the good fitting hole and you just cut the sheet so the hole ends up in the right place. I would want a slightly larger pipe attached to it so you pipe went thru that and you could get insulation closer to it. But it looks like you have a very low roof so working in there might be a treat. 

Others that Know more about this might be along.


----------



## Snoonyb (Jul 26, 2017)

DO NOT install a solid cover over the hole until you are absolutely certain that is not required combustion air.

Be cognizant of where the people who are giving you advice are from, their views may be of their local experience.


----------



## Snoonyb (Jul 26, 2017)

Toddxx77 said:


> Yes it is on the south west side, no curtains just blinds, the window faces south and the room and windows is shade by a tree on the south side. Outer wall facing west is brick. But I have checked the temp on the walls and the temp is the same as the other rooms.



Thanks.

Check the temp at the windows. while glass is an excellent insulator, it is as well an excellent conductor.

Installing a ceiling fan to better conduct the conditioned air in the room may be your solution.


----------



## slownsteady (Aug 2, 2017)

Snoonyb said:


> ...while glass is an excellent insulator, it is as well an excellent conductor....


Can't be both:down:


----------



## Snoonyb (Aug 2, 2017)

Look it up.


----------



## nealtw (Aug 3, 2017)

slownsteady said:


> Can't be both:down:



I conducts light, don't ya know.


----------



## slownsteady (Aug 3, 2017)

A pane of glass vs. fiberglass. perhaps. But they are two different things.


----------



## Snoonyb (Aug 3, 2017)

Look it up.

Ever seen a glass beaker with boiling liquid, above a bunsen burner?

Then there are dual and triple glazed windows and 1-1/4 plate glass in commercial buildings.


----------



## nealtw (Aug 3, 2017)

Snoonyb said:


> Look it up.
> 
> Ever seen a glass beaker with boiling liquid, above a bunsen burner?
> 
> Then there are dual and triple glazed windows and 1-1/4 plate glass in commercial buildings.



Hell, I thought you were joking. Glass has an R value.


----------



## Snoonyb (Aug 3, 2017)

If you heat glass hot enough, it will even conduct electricity.


----------



## nealtw (Aug 3, 2017)

Snoonyb said:


> If you heat glass hot enough, it will even conduct electricity.



Yeah that's why they never put fuses in glass.:rofl:

Molten glass has different properties than  what we would know as glass. 

Silly adds no good info to a discussion.


----------



## Snoonyb (Aug 3, 2017)

See post #11.

It can and is both.


----------



## bud16415 (Aug 3, 2017)

slownsteady said:


> A pane of glass vs. fiberglass. perhaps. But they are two different things.



https://www.thoughtco.com/what-is-fiberglass-820469


Fiberglass is not the insulator. What is the insulator is the trapped air between the fibers. 

Glass windows some have higher R values not because of the layers of glass but because of the inert gas trapped between the layers.


----------



## Snoonyb (Aug 3, 2017)

Then, when you are immersed in the insulator aspect of glass, which it is, there is the fiber-optics element.


----------



## slownsteady (Aug 5, 2017)

Welcome Todd, by the way. i hope we have answered your question. And I hope that our rambling side discussion hasn't turned you off to the site. If you need more specifics, ask away....this is your thread.


----------

