For a house constructed over a crawlspace, how many square feet of ventilation is required for a 30' x 50' building with a class 1 vapor retarder?

To determine the required square footage of ventilation for a house constructed over a crawlspace with a class 1 vapor retarder, one must consider the Virginia Residential Code, which specifies ventilation requirements based on the area of the crawlspace and the type of vapor retarder used.

In this scenario, the crawlspace ventilation should be calculated based on the crawlspace's square footage. The formula typically used is that for every 150 square feet of crawlspace area, there should be at least 1 square foot of ventilation.

For a building with dimensions of 30 feet by 50 feet, the total area of the crawlspace would be:

30 ft x 50 ft = 1500 sq ft.

Given the requirement of 1 square foot of ventilation for every 150 square feet of crawlspace area, the calculations would follow as:

1500 sq ft / 150 sq ft = 10 sq ft of required ventilation.

However, because the question indicates that the structure features a class 1 vapor retarder, the guidelines differ. For a crawlspace with a class 1 vapor retarder, the requirement potentially changes. Depending on local amendments or specific interpretations, if the crawlspace is deemed to have minimal moisture intrusion, the ventilation can be