The issues that he pointed out to be addressed are correct but his assessment is not.
Adding supply air from the HVAC system into the crawlspace will not pressurize the space greater than the living space above as the supply air duct also discharges into the house.
Air cannot move across the building envelope opening without a pressure differential. The supply air system cannot pressurize the crawlspace greater than it is pressurizing the living space.
He stated that closing the foundation ventilators with the HVAC running depressurized the crawlspace by one Pascal. How does negative pressure air enter a positive pressurized house?
I am also confused!
[size=2]Increasing the size of the air-conditioning unit will not remove more moisture, the unit must be undersized to remove moisture.
Air leaks in the return will pressurize the interior of the house and draw in contaminants from the crawlspace. Adding supply air ducts to the crawlspace will depressurize the interior of the house that the return is trying to pressurize. It’s not as big a deal as he’s making it.
Blowing air-conditioned air into the crawlspace that does not have a cooling load causes increased amounts of condensation to occur within that space. He claims evidence to support a water source in the crawlspace. ??
When you seal off the crawlspace you want to pressurize it by taking in air from the exterior, passing it through the HVAC system to remove moisture and discharging it into the house/crawlspace.
Attempting to depressurized the crawlspace with a fan, sucks in moisture from the exterior leaks in the crawlspace and promotes moisture to accumulate in the crawlspace still.
He even said; "Clearly, even with the blocked vents, the crawlspace was relatively leaky and would need air sealing. "
[/size]He made some changes in the environment, but he wasn’t 100% successful because of these inaccurate perceptions.
Why did he not properly seal the air duct system before he went out and excavated the foundation and added insulation (?) To the exterior of the house?
They still have a 150 CFM air leak after all the work was done!
He sealed up the penetrations in the floor from the house. This was a waste of time as pressurizing the duct supply needs a path to enter the crawlspace anyway. Another waste of time and money.
Why is it even necessary to seal the crawlspace air from the house interior when you’re depressurizing the crawlspace? The air is not going to enter the house with the fan running.
[size=2]I see nothing about installing a vapor barrier in the crawlspace to prevent moisture from the soil. Does he think drainage tiles are going to keep the moisture out of the crawlspace?
He talks about air pressure, but he doesn’t seem to understand vapor pressure. You change the vapor pressure in the crawlspace and it doesn’t matter what you do to the drainage on the exterior of the house, you’re still going to pull moisture in from subterranean sources.
This is not a structural issue, it’s an indoor air quality problem. I can guarantee you they spent more time/money digging up the foundation than addressing indoor air.
Did they resize the HVAC system which is now grossly oversized and cannot control humidity within the house (especially when they removed the latent heat loads in the crawlspace from the system)?
What is your assessment Jim?