CRC compliance for wall assembly U-Factors

[DRAWZILLA]

1 hour ago, Richard_Morrison said:

There is some misinformation here that should be corrected. OF COURSE, we all need fresh air in our houses. The problem is that during extremes of heat or cold, when we WANT the windows shut to save on heating or cooling costs, just opening a window or having a leaky house causes us to spend FAR more to get that fresh air in energy costs. We pay a huge premium for fresh air in temperature extremes by using the "open window" method. By using an HRV or ERV system, we can get the same fresh air for much reduced energy cost, as well as giving us more control over the humidity. Hot fresh air or cold fresh air is not cheap.

 

In general, we want neutral or slightly positive pressure in our houses. Negative air pressure causes backdrafts and problems with gas appliance starvation. Hence the need for adequate makeup air. Negative air pressure (even slight) is unhealthy, and may even kill us in some circumstances. 

Never seen or heard that anywhere and apparently neither has the state of California.

[Richard_Morrison]

1 hour ago, DRAWZILLA said:

Never seen or heard that anywhere and apparently neither has the state of California.

Except maybe for the requirement of makeup air in the California Mechanical Code, Sec. 505.5.

 

EDIT: Here's a discussion of negative air pressure: http://www.cwsuter.com/negative-air-pressure-symptoms-dangers-solutions/

[DRAWZILLA]

1 hour ago, Richard_Morrison said:

Except maybe for the requirement of makeup air in the California Mechanical Code, Sec. 505.5.

 

EDIT: Here's a discussion of negative air pressure: http://www.cwsuter.com/negative-air-pressure-symptoms-dangers-solutions/

Richard, that is just a company trying to sell a product not anything to do with the code we need to follow, it's their opinion. I didn't see any reason to do it their way. It costs more than using an always on fan that doesn't create enough negative air to make people sick like you think. Of course it's preferred to have all that built in to your system , but not everyone wants to pay more.  a slight Negative air in your home is better than having it air tight any day. That's a fact Jack.

[Richard_Morrison]

4 minutes ago, DRAWZILLA said:

Richard, that is just a company trying to sell a product not anything to do with the code we need to follow, it's their opinion. I didn't see any reason to do it their way. It costs more than using an always on fan that doesn't create enough negative air to make people sick like you think. Of course it's preferred to have all that built in to your system , but not everyone wants to pay more.  a slight Negative air in your home is better than having it air tight any day. That's a fact Jack.

Okay, then here's a general information site, with nothing specific to sell: http://www.chimneys.com/articles/negative-house-pressure-can-cause-multiple-problems

A negative air pressure in a home with fuel-based appliances can kill you. That's the reason that carbon monoxide detectors are now mandated in homes. https://www.forbes.com/sites/marijkevroomendurning/2013/08/20/carbon-monoxide-a-silent-killer-are-you-safe/

https://www.abe.iastate.edu/extension-and-outreach/carbon-monoxide-poisoning-downdrafting-aen-165/

 

Your attitude that a negative air pressure in a home is somehow a good thing violates the Mechanical Code, and is extremely dangerous thinking. It does not take a large negative pressure to move carbon monoxide the wrong direction. Even a slight negative pressure will do it.

[DRAWZILLA]

A slight negative air pressure as most typical fans do, doesn't kill anyone and the testing proves it. The state of California allows it and the rest is just your opinion. or you are just trying to sell something.

[Richard_Morrison]

9 minutes ago, DRAWZILLA said:

A slight negative air pressure as most typical fans do, doesn't kill anyone and the testing proves it. The state of California allows it and the rest is just your opinion. or you are just trying to sell something.

In Southern California, it's not usually dangerous, because windows are frequently open, and negative pressure from exhaust fans is neutralized. A bath fan running at 80 cfm is probably counteracted by modest house infiltration. A professional-style kitchen exhaust hood running for awhile at 1000 cfm is an issue in a tightly sealed house. However, baldly stating that the "State of California allows it" does not make it so. If you've got a Code section that allows it, cite it. I've cited the section that requires makeup air, and this is not my opinion. Bad health effects from negative air pressure are not my opinion, either. So, either produce an authority that says negative air pressure is no big deal, or stop trying to convince everyone that a very bad construction practice is okay.

[DRAWZILLA]

maybe bad architecture is ok then.

[Alaskan_Son]

Here in Alaska and in other cold northern climates its actually imperative that houses remain under negative pressure.  Yes, negative pressure has its health risks, but this is something we've just had to learn to balance and deal properly with.  As soon as a house is under positive pressure here, we get condensation and the resulting mold and rot inside our walls, floors, and ceiling assemblies.  Its actually a really really big deal here and codes have all been amended to completely remove supply only ventilation systems for this reason. 

 

Actually, even the warmest regions in Alaska have essentially (if not literally) zero cooling degree days and so there is almost always a constant negative pressure anyway simply due to natural air leakage and the stack effect.

[Richard_Morrison]

20 minutes ago, Alaskan_Son said:

Here in Alaska and in other cold northern climates its actually imperative that houses remain under negative pressure.  Yes, negative pressure has its health risks, but this is something we've just had to learn to balance and deal properly with.  As soon as a house is under positive pressure here, we get condensation and the resulting mold and rot inside our walls, floors, and ceiling assemblies.  Its actually a really really big deal here and codes have all been amended to completely remove supply only ventilation systems for this reason. 

 

Actually, even the warmest regions in Alaska have essentially (if not literally) zero cooling degree days and so there is almost always a constant negative pressure anyway simply due to natural air leakage and the stack effect.

While you don't want to drive moisture-laden air into walls in very cold climates, of course, usually up to about 3 pascals of pressure isn't an issue, and introducing pressure-relief is pretty easy, in any case. Negative house pressure seems to be a significant issue related to radon in many parts of Alaska. http://www.epi.alaska.gov/bulletins/docs/b2015_25.pdf Ideally, you want a zero-pressure house with adequate fresh air exchanges.

[Alaskan_Son]

3 minutes ago, Richard_Morrison said:

Ideally, you want a zero-pressure house with adequate fresh air exchanges.

 

Yes, I agree, zero pressure would be ideal but its not realistically feasible from any practical standpoint.  In erring to the side of caution I will always put my house under negative pressure before I put it under positive pressure. 

 

Anyway, only reason I bring it up is that your assertions that slight positive pressure was better is really only true in warmer climates.  In colder climates, the opposite is true.  And in all cases, I think we can agree that zero pressure is best, once we start introducing all the variables to the equation though its just not something that's going to happen anytime soon.