951 Floors Over Crawl Spaces

The situation is a little different for a floor directly over a crawl space. The problem is that knowledge of the temperature of the crawl space is necessary to perform the calculation. But the temperature of the crawl space is dependent on the number of exposed crawl space surfaces and their U-factors, as well as the impact of crawl space venting, if any. For design-day heat loss calculations, it is usually most expedient to assume a crawl space temperature equal to the outdoor design temperature. This will very nearly be the case for poorly insulated or vented crawl spaces.

When actual, rather than worst-case heat loss is needed, it is necessary to perform a heat balance on the crawl space. The process is described in the ASHRAE Handbook of Fundamentals. Below is a brief summary of the approach.

Metal Roof Panel

\ Purlin

1" polyisocyanurate Figure 9.20 Insulation suspension system.

\ Purlin

1" polyisocyanurate Figure 9.20 Insulation suspension system.

Table 9.8 "Roll runner" method

Mfgr's

Nominal

Over the

Roll

Roll-Runner

Rated

Thickness

Purlin

Runner

with Insulated

R-Value

(Inches)

Method

Method

Purlin

0 0

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