Thread: Unheated Basement Ventilation

Unheated Basement Ventilation
Hi everyone;
I am just starting out and have a question about an unheated basement. There is not any outside ventilation to the basement visible. The basement has a concrete floor. My question, is this to be treated like an unheated crawspace and requires vents to be installed or a fan to vent the area?
Thanks
Barney Cheeseman

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Unless the space can meet provisions under section R408.3 for unvented crawl space, I would treat this like any other underfloor space and require ventilation and ventilation openings as prescribed under R408.1 and R408.2.

Originally Posted by Barney Cheeseman

Unheated Basement Ventilation
Hi everyone;
I am just starting out and have a question about an unheated basement. There is not any outside ventilation to the basement visible. The basement has a concrete floor. My question, is this to be treated like an unheated crawspace and requires vents to be installed or a fan to vent the area?
Thanks
Barney Cheeseman

Mr. Cheeseman:

I would first consider whether the height of the space meets the requirements of a basement or crawl space. I agree with your idea of ventilation, however it differs quite a bit depending on which case you are dealing with, and what the construction type is as well.

As I come from Northern country, crawl spaces (once defined as such) require insulation either on the walls of the crawl space to a specific distance below ground level or the floor above needs insulation between the floor joist system with then necessary vapor barriers and or other approved vapor barrier material. Ventilation is quite different for both cases.

For slabs on grade, either insulated walls or floors in a similar manner to above, with a vapor retarder below the concrete slab per Code. The ventilation again is different depending on the layout of the crawl space. One thing that hasn't been mentioned, is there any access from the crawl space directly to the main basement of the home (if a full or partial basement exists), and if so the ventilation again is different as well as the insulation technique to reduce heat losses.

I think that to properly get a full picture of the crawl space and ventilation you might want to read ICC-ES IRC 2006 or 2009 Code, and the 2006 or 2009 Mechanical and HVAC Code to know what both are requiring in these instances. In this way you will have a better understanding of what needs to go into these areas (for heating), and what needs to go out of these areas (for ventilation and circulation), which will help answer your questions.

I hope this help you.

Dwight Walker

Forget the articles. If it is a full unheated basement I see no reason for ventilation unless the crawl is suspect to moisture or other concerns.

As most folks up north know the vast amount of homes with non living space below such as full basements, not crawl spaces are never ventilation unless there is a problem. A sealed crawl space that is done properly and sealed off with plastic and such needs no ventilation. A full basement with concrete foundation walls and floors is far more sealed off than a sealed crawl space is.

Insulation on the underside of the first floor would be in order, paper side up.

Again, unless there is an existing concern (which should be taken care of anyway) I see no call what so ever as long as we are not talking a stacked stone wall and dirt floor basement.

For what you describe, it sounds like a basement and ventilation should not be needed but you are in Utah and I'm in Pennsylvania so I don't know how things work there. But around here, open vents to crawlspaces typically have too many drawbacks to be beneficial. Our summers get so humid that ventilating a crawlspace often times allows more moisture in than it gets out. I recommend sealing the vents on nearly every crawlspace I see.

Thanks to all for the an informative feed back, has been very helpfull.

Ventilation is over rated. If the vapour barrier is in place on the floor and the walls are properly insulated ventilation proves to be of no value. I agree with Ted and Nick.
Check out this study http://www.cmhc-schl.gc.ca/publicati...ech/90-231.pdf

Originally Posted by Steven Bowman

Ventilation is over rated. If the vapour barrier is in place on the floor and the walls are properly insulated ventilation proves to be of no value. I agree with Ted and Nick.
Check out this study http://www.cmhc-schl.gc.ca/publicati...ech/90-231.pdf

It may be over rate but you best call it out where it is missing and required by code or you will be the bad guy when mold starts growing.

Originally Posted by James Duffin

It may be over rate but you best call it out where it is missing and required by code or you will be the bad guy when mold starts growing.

I have to agree with James. The drawings in the article show the vents blocked off by the insulation rendering the vents ineffective . Here in the NW we require baffles when vents are placed in floor joists bays to maintain air flow .

First off, your first post and no introductions. Hello, welcome.

Please update your profile and tell us something about yourself, are you a student, a Home Inspector, AHJ, contractor, Homeowner, future homeowner, tenant, DIYer, what? WHERE in Utah?

You say "just starting" but not assuming as an HI, perhaps your reference is your having just joined and making your first post, which doesn't tell us anything.

Next, what is and is not required or what constitutes a basement DEPENDS on a LOT, some of which has been covered, some of which has not. You tell us nothing really about either the circumstances, even if it is a residence, a multifamily structure with a common basement, a commercial space, ag, church, quasi-public building, a "bomb shelter", type or age of the structure, changes to basement - past, or intended, nothing.

Your question is extremely VAGUE.

Depends.

What's IN the basement?

IS IT A BASEMENT, and a Basement for WHAT.

Operable windows? Doors to exterior?

What is present in this "basement"?
Mechanicals? Systems serving the habital or occupied space above? Laundry? Storage tanks, etc. Fuel fired appliances? Fire places? Chimneys? Clean outs? Sumps? wells? Electrical? Plumbing?

"Unheated" not sure what THAT really means, or why that would matter, heck there are homes that are have no central "heating system" - and if not habitated, and mostly underground - wouldn't need a "heated basement" even to habitate it, let alone OCCUPY it, depending on where in the WORLD it was located.

Is the space finished? Room to work? Storage? What is being stored?

Purpose...storm or emergency shelter?

What's the access to the basement? (from interior of home, exterior only, both, neither, doors, scuttles, permanent stair or ladder, no permanent ladder, through the floor scuttle, etc.).

Are you asking about infiltration, operable windows, exhange of air to be occupied (not habital) space?

Make-up air for exhausting? combustion air for fuel fired appliances? WHAT?

Next, what is the purpose of the question?

Originally Posted by James Duffin

It may be over rate but you best call it out where it is missing and required by code or you will be the bad guy when mold starts growing.

James, I always note ventilation status and refer to the codes recommended values as it pertains to the type of crawlspace.

Read this!

BSI-009: New Light In Crawlspaces — Building Science Information

Originally Posted by Raymond Wand

Read this!

BSI-009: New Light In Crawlspaces — Building Science Information

Raymond I agree. I have seen similar here. The best way is to properly insulate the walls in addition to the properly installed floor vapour barrier. IMO insulating the main-floor joist bays is not beneficial and we see it causes problems. Most of the time the floor joist insulating is not completed properly anyway.

Great article and great website Mr. Bowman!

+1 on the article. Good info.

Steve; Thank you for your input & the valuable information from the artical & the web site! From this artical, the things I was taught in courses on ventilation and insulation I have taken, makes me take another look at their reasoning.
Thanks again
Barney

Originally Posted by Fernando Fernandez

Great article and great website Mr. Bowman!

Thank you Fernando, no need to be so formal. Call me Steve.