Ventilation crawl space, design

Based on our experience with remedial actions and modifications of design in new construction we recommend the following strategy for making new buildings (slab on grade, ventilated crawl space or furnished basement) radon protective or radon safe in a cost-effective way ... 

Minimize the contact between living area and subjacent soil. Buildings with slab on grade or ventilated crawl space require less modification of the standard design than houses with basements. If basements cannot be avoided on radon dangerous soil, it is recommended to keep the basement separated from the living space by normally closed doors and if possible, install exhaust ventilation from the basement. 

Current standards recommend radon levels of 4 pCi/1 or less. Methods to prevent buildup of radon concentrations include ventilating crawl spaces, drain tiles in foundations and other locations. Assessment of constmction sites for radon and control methods for radon are an important element of facility design and real estate transactions. 

Figure 2. Radon protective design crawl space provided with a slab, mechanical supply exhaust ventilation of living space and crawl space.

Table III. Distribution of Measured Radon Concentration in 24 Detached Houses Designed with Mechanical Exhaust Ventilation through the Crawl Space...

Flat Bottoms Flat bottom vertical cylindrical tanks present particular problems. The bottom must be so constructed and supported as to be completely rigid and well ventilated from the sides and underneath. This may usually be provided by I beams. The bottom shall be tack welded to the I beam so that the bottom will not flex and crack the lining when it is installed. (Reference 8, p 74). The maximum free span between I beams can be calculated on the basis that the maximum deflection under full load conditions shall not exceed the free span divided by 1000. However, in the case of vessels containing only gas at atmospheric pressure and no internal spheres, then the deflection can be as great as the distance divided by 500. It is good design to leave sufficient space between I beams to allow for maintenance perhaps enough space for a man to crawl between them. 

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