[harpua728]

I have a louvered bifold door leading to my basement (which I may chane to a solid door) and I've noticed that every time the gas furnace turns on, the door moves/shuts. I've been reading up on combustion, venting, air intake, etc and I want to make sure that this is somewhat normal.

The basement is unfinished and the windows have vents that are taped shut (by the previous owner) but are not air tight. The furnace is located underneath my fireplace and is vented into the chimney. However, I'm not sure if that's intake, exhaust, or both. The boiler room is enclosed by some cheap paneling and is not air tight.

I'm thinking about finishing my basement which would change things as I would replace the windows and do a better job insulating the entire area.

What do I need to take into consideration as it applies to proper fresh air for the furnace. Any help would be appreciated as I clearly know little to nothing about this.

If you need more info, or pictures, I'll me glad to provide them.

Thanks for your help

 

[raylo32]

The pros will chime in soon, but I can tell you that if the appliances draw air from the space they are installed in there are minimum volume requirements and your louvered door is probably required to meet the code by communicating with a larger space. Using a solid door in that situation could likely lead to an unsafe condition.

 

[WhatRnsdownhill]

is it a hot air furnace or boiler with water in it?

 

[harpua728]

hot air furnace

 

[WhatRnsdownhill]

just make sure they arent using that louvered door as your house return, being that its moving when the furnace turns on...

 

[harpua728]

Since most of this will be based on formulas I took some measurements.

My utility room has a 120,000 Btuh furnace and a 35,500 Btuh water heater. In a complete different section of my basement, I have a gas dryer (22,000 Btuh).

The furnace and water heater need 7,750 cubic feet of air intake (50x(120+35)). The boiler room is only 840 cubic feet but it's not entirely sealed off from the rest of the basement as there are big gaps high in the walls between that room and the rest of the basement. Plus, I keep that door open constantly. The ENTIRE basement measures only 3,780 cubic feet so even if the furnace is drawing air from the entire basement, it still needs more, and this is probably why I the door that leads to the basement keeps moving when the furnace turns on.

Is this condition considered safe?

The basement windows have vents that are taped shut (pictured below). The previous owners did this but I never knew what the reason was. Are those vents needed for the furnace to operate properly? Even though they are taped shut they are definitely not fully sealed and air is still getting through.

Furthermore, if I finish the basement, I would replace these windows and do a better job of sealing/insulating the basement. May this cause problems as well?

 

[harpua728]

just make sure they arent using that louvered door as your house return, being that its moving when the furnace turns on...

I'm not sure what you mean by this but there are return vents throughout the house if that helps

 

[WhatRnsdownhill]

ok first we are talking about 2 different things...combustion air is one and return air is 2nd... first the return air...the door could be moving because hot air furnaces push air out the heating registers in all the rooms, and usually in the hallway ceiling or wall there is a big grate where a filter can also go for the air that the big fan in the furnace pulls the air that is pushed out the registers...do you see anything like that big grate in the house?

 

[harpua728]

There is no big grate that I see in the house. I know some homes have this in the upstairs hallway ceiling but we don't. We just have return air vents spread out throughout the house.

 

[beenthere]

If you finish the basement. You'll need to add combustion air intakes from the outside to your furnace room.

 

[SPS-1]

You say your basement is 3780 cubic feet --- so about 472 sq ft. How big is your house? I am no pro either but that sounds like a darned big furnace.
Just the same, surprised just the draw of combustion air is moving a door.

 

[harpua728]

The house is 1,900 sq ft. The basement may be a little larger than I stated as I didn't factor in a large cedar closet.

 

[jimn]

Furnace dies sound to large for a house that size unless you live in Churchill Manitoba . The furnace will draw combustion air but it should be enough to close a door. I would look for leaks in the return ducts or a blower door on the furnace not close properly

 

[TheEplumber]

I'm not sure what you mean by this but there are return vents throughout the house if that helps

Are you sure these are not supplies?
Where are the returns located?

 

[veesubotee]

Don't know if this applies in your case, but FWI:

I had a great rush of air under my door to the basement when the heat was on. Using a 'tell-tale', I probed all of my basement return ducting and found a (hidden) big leak, which was promptly fixed and cured the problem.

V

 

[harpua728]

Are you sure these are not supplies?
Where are the returns located?

They are on the walls about 6 inches off the floor. Same goes for the supply vents. They are both located on walls just off the floor. Some blow and some suck.

 

[harpua728]

Don't know if this applies in your case, but FWI:

I had a great rush of air under my door to the basement when the heat was on. Using a 'tell-tale', I probed all of my basement return ducting and found a (hidden) big leak, which was promptly fixed and cured the problem.

V

Where was the leak and how did you find it?

 

[windowguy]

If you finish the basement. You'll need to add combustion air intakes from the outside to your furnace room.

Is this an absolute statement? are you saying every single basement that is "finished" needs outside air for combustion? Or did you just say that off the size of his mechanical room? My furnace was replaced and I am I not pulling in combustion air from outside my finished basement. Matter of fact I replaced the louvered door with a solid core door and added a "high vent" and "low vent" from the mechanical room to the main finished basement room with grates between the walls This all passed inspection. (yes I know not all inspectors are the truth). But I'm pretty sure I even read it on the board here a decade ago about the "high vent low vent" thing for air circulation.

 

[Bud9051]

One of the problems with these simplified guidelines is they don't address the real problem. You can have a huge basement that is sealed up very tight and thus has insufficient combustion air. Just because one approach works in one house doesn't mean it will work in another.

The idea of supplying outside combustion air for all combustion appliances is definitely good as it ensures the replacement air will not be sneaking through the many leaks around the house. Until we switch to sealed combustion appliances or eliminate the combustion inside our homes we should be providing an outside source for that air regardless of codes. In this the codes are definitely a minimum.

Bud

 

[harpua728]

If outside combustion air is brought into the boiler room, will it prevent the furnace from pulling through other leaks in the house if the house/basement is not tight? Basically, what I'm asking is will the furnace automatically pull all the combustion air from the outside supply line rather than using other sources?


On a side note, since the furnace is currently pulling air from other parts of the house, what is stopping it from pulling air from the water heater exhaust valve since that is technically an open supply line to fresh air (via the chimney)?