Thermal and Moisture Protection

Question 1

Layers of a green roof

Answer 1

1. Plants
2. Engineered soil or growing medium
3. Filter fabric
4. Retention layer
5. Drainage layer
6. Sheet barrier
7. Waterproof membrane

Question 2

3 Types of Green Roofs

Answer 2

1. Intensive: 1’ soil depth for shrubs, trees, etc.; require irrigation and drainage systems; heaviest; requires concrete deck.
2. Extensive: 4-6” soil depth; low maintenance small, hardy plants; medium weight; installed over any properly designed roof.
3. Modular: Trays with 3-4” of engineered soil and low growing plants; installed over pads; lightest weight.

Question 3

Layers of flat roof assemblies

Answer 3

1. Wear course (aggregate or pavers)
2. Drainage layer
3. Roofing membrane (built up or single ply; sloped 1/4” per foot min)
4. Thermal insulation (3 options for placement)
5. Vapor retarder (on warm side)
6. Roof deck

Question 4

Three positions of thermal insulation in flat roof assembly

Answer 4

1. Below the roof deck
2. Between roof deck and roofing membrane
3. Over the roofing membrane

Question 5

Built-Up Roofing System

Answer 5

1. Wear course of gravel

2. Alternating layers of asphalt or tar and reinforced felt

Question 6

Single Ply Roofing System

Answer 6

Types: TPO, PVC, Modified Bitumen, EPDM. Applied in liquid or sheet form. No slope limitation. Thin, flexible and strong.

Question 7

Roof drainage rules of thumb

Answer 7

Slope roof min 1/4” per foot. Slope gutters min. 1/16” per foot. Minimum 2 roof drains per 10,000 SF roof area + 1 per 10,000 after that. Downspouts: 1 square inch per 100 SF of roof area.

Question 8

Vapor retarder

Answer 8

Material of low permeance installed in a building to prevent moisture from entering and reaching a temperature where it can condense into a liquid. Install on warm side in cold and temperate climates. Install on outer face of construction in warm climates. Sometimes inherent or included in rigid foam insulation boards.