4-32. To  be  effective,  reflective insulation  must  have  what  minimum air  space? 1. 1/2 in. 2. 3/4 in. 3. 1 in. 4. 3 1/2 in. 4-33. Rigid insulation may be used for which  of  the  following  structural purposes? 1. Sheathing  and  building  boards only 2. Building  boards  and  roof decking  only 3. Roof  decking  and  sheathing  only 4. All of the above 4-34. Which  of  the  following  substances is sometimes mixed with plaster to reduce  heat  transmission? 1. Vermiculite  or  perlite 2. Rock or glass wool 3. Sawdust 4. Shredded  bark 4-35. To  reduce  moisture  and  protect  wood frame members, what type of material should you use as ground cover in crawl spaces? 1. Roll roofing only 2. Polyethylene  only 3. Roll  roofing  or  polyethylene 4. Blanket  insulation 4-36. When structures are built on slabs, it is a good practice to install a vapor barrier under the slab. 1. True 2. False 4-37. When insulation is used without a vapor  barrier,  what  material  is normally used to envelop the entire exposed  wall  and  ceiling? 4-38. When  placing  fill  insulation  over ceilings,  which  of  the  following devices should you use to ensure uniform  thickness? 1. Carpenter’s  level 2. String line 3. Bottom  board 4. Leveling  board 4-39. Which  of  the  following  materials are  effective  vapor  barriers against   condensation? 1. Aluminum  foils  only 2. Asphalt-laminated  papers  only 3. Plastic  films  only 4. Each of the above 4-40. The  system  in  which  wall-height rolls of plastic film are applied to produce a positive seal against water vapor is known by what term? 1. Enveloping 2. Vapor  proofing 3. Moisture  proofing 4. Positive  sealing 4-41. What is the most practical way to remove  moisture  from  roof  spaces? 1. Heating the air 2. Adding  more  insulation 3. Ventilating 4. Installing  a  dehumidifier 4-42. How are hip roofs best ventilated? 1. By  inlet  ventilators  along  the rake and outlet ventilators along the soffits 2. By inlet ventilators along the ridge and outlet ventilators along the soffits 3. By inlet ventilators along the soffits  and  outlet  ventilators along the ridge 4. By inlet and outlet ventilators along the ridge 1. Building  paper 2. Plastic  film 3. Building  board 4. Fiber glass 22