Automatic garage ventilation

[strutaeng]

The post by hughfree was excellent! Much light on the subject.

I also read something about what the OP read about future building codes, so I installed this:
http://www.rewci.com/10-inch-shutter-fan-with-cord.html

I was also worried about fumes entering my home from my car after it gets shut down. I looked into wiring to my garage door opener, but I think there was a need for some sort of timer and relay...in the end I never wired it like that.

I do however, use the fan quite a bit: when welding, sanding and spray painting. And yes, it works better if I'm working close to it to evacuate the dust, smoke or spray mist. I usually crack the garage door opener to get some intake, otherwise it wants to **** the conditioned air from my house through the door gaps.

I hope this helps.

 

[wssix99]

but if CO fumes tend to sink

I don't believe they do. The codes don't specify where vents need to be and most of the CO sensors I've seen have been on ceilings.

 

[hughfree]

Guys,
I have just noticed all of the questions regarding the OP's design. I am headed off to work at the moment and will respond tonight of tomorrow AM.
Sorry....

 

[hughfree]

Good post. Thanks for the info.

How would you design a system for the OP's garage? It sounds like you may be recommending that he use his fan to **** in outside air and put an exhaust grille somewhere for the air to get pushed out of. A possible problem with that approach would be if the situation led to positive pressure in the garage and actually pushed contaminants into the house. Given that he's primarily trying to get rid of exhaust fumes, what are the ideal locations for the intake and exhaust locations whether pushing or pulling with the fan?

DC

There are multiple components to car exhaust fumes...many are heavier than air. Carbon Monoxide is the main reason some local code requirements are requiring automatic garage ventilation. They are trying to address the chance for lethal levels of CO building up. The smelly part NOx, HC's, will lay on or near the floor. A ceiling level exhaust fan will help with CO levels since it will tend to rise and distribute evenly. The stuff that we all notice is harder to address. The best way is to leave the garage door open for a little while and the concentration levels will dissipate. In colder climates allowing a garage fan to run while you exit the car and enter the house will work (air will be drawn from the house into the garage). The smelly stuff will still be in the garage for a while but shouldn't bother you in the house. Other solutions for attached home garages become impractical and expensive (i.e, source capture, cross draft, push-pull to name a few).

 

[hughfree]

That's a good question. I put the fan in the ceiling, but if CO fumes tend to sink, maybe it should be down by the floor? I figured that hot exhaust fumes would rise, so the ceiling vent should take care of it before they cool. I'm not really all that worried about CO; more about the odor of the exhaust. If CO sinks, I'm good, because the house is 20" higher than the garage floor.

Unfortunately CO rises....but generally will not reach a dangerous concentration level in the house without an appliance failing, mis-application, or deliberate action.

 

[hughfree]

I think the point of the ASHRAE equation is to economize air changes and only estimate the air movement required to keep CO below a certain concentration.

The formulas don't clear out all the funk in the air because they don't do full air changes - just enough to get the CO out that is being produced over time.

For my garage, I also have the HRV hooked up to the regular switch lights so the air is changing while I'm working in there. I can also turn on the fan if I want better air quality than the timers on the garage door opener lights provide. (With regard to the fan running on those timers - I want the fans to run at a minimum for electricity and heat economy. Just enough to meet code.)[/QUOTE]