HVAC Supply/Return Requirements in Basement/Crawlspace

[Kalmady]

8’ tall basement (unfinished but conditioned), there’s a section of the basement that jumps to a 4’ tall crawlspace (also unfinished but conditioned). There is no wall or obstructions between the 8’ & 4’ sections and there is one HVAC supply & return in the 8’ tall portion of the basement.

Inspector is requiring a second supply in the crawl space section of the basement.

From everything I’m reading this isn’t required because there’s no wall between the 8’ portion & crawl space. I would agree one would need to be added (or at the very least a transfer grill) if there was a wall between there.

Thoughts/opinions?

 

[e hilton]

Why does he care if there is hvac in the basement? Did he mention a code section?

 

[Kalmady]

This is one of the worst inspectors I’ve ever had to deal with and throws a lot of his own requirements at you.

He referenced R408.3

 

[RFM132]

If the crawl space is unvented, a supply might be required to meet the 1 cfm of supply air per 50 square foot of crawl space area requirement.

 

[Kalmady]

If the crawl space is unvented, a supply might be required to meet the 1 cfm of supply air per 50 square foot of crawl space area requirement.

But aren’t I vented because I’m open to the full height basement and there is a door at the top of the stairs.

 

[RFM132]

No. A vented crawl space would be outside of the thermal envelope with exterior ventilation openings. If you are making the case that the basement and crawl space area are sufficiently conditioned by one return and one supply, that would become more of a Manual J and Manual D design issue for the HVAC system. The main concern would be that an undersized HVAC system would create temperature differentials between the two spaces great enough to result in a moisture issue.

 

[ADAguy]

Good technical answer

 

[ICE]

No. A vented crawl space would be outside of the thermal envelope with exterior ventilation openings. If you are making the case that the basement and crawl space area are sufficiently conditioned by one return and one supply, that would become more of a Manual J and Manual D design issue for the HVAC system. The main concern would be that an undersized HVAC system would create temperature differentials between the two spaces great enough to result in a moisture issue.

Too technical an answer. The odds of this being the issue with the OP’s inspector are slim to none.

 

[ICE]

8’ tall basement (unfinished but conditioned), there’s a section of the basement that jumps to a 4’ tall crawlspace (also unfinished but conditioned). There is no wall or obstructions between the 8’ & 4’ sections and there is one HVAC supply & return in the 8’ tall portion of the basement.

Inspector is requiring a second supply in the crawl space section of the basement.

From everything I’m reading this isn’t required because there’s no wall between the 8’ portion & crawl space. I would agree one would need to be added (or at the very least a transfer grill) if there was a wall between there.

Thoughts/opinions?

What reason did the inspector provide? What is the square foot area involved?