To expand further on roof venting and insulation, it’s critical to understand that roof venting will depend directly on climate. This rule holds true when venting a roof deck or an entire attic.
What is the purpose of roof ventilation, you ask? In colder climates, roof ventilation is intended to help maintain a cold roof temperature to prevent ice dams that occur when snow melts and re-pools on the roof.
In warmer climates, ventilation is used to relieve solar heating from the roof or attic to improve cooling efficiency in a building. This will help to greatly reduce strain on an air-conditioning system.
In mild climates with cold and warm seasons, ventilation can serve both purposes.
If a home has an air-conditioned attic or is designed with vaulted ceilings, residential building codes may require a roof deck to be vented from eave to ridge. When venting a roof deck, codes will call for a minimum of 1 inch of air between roof sheathing and the top of insulation, as mentioned above.
However, most experienced roofers will agree that this minimum requirement is far from adequate. For better performance in roof ventilation, air space is recommended at 2 inches deep at a bare minimum.
Venting in this manner may decrease the capacity for insulation in an attic, but it will prevent the common issue of limiting the amount of air that can circulate underneath a roof.
In order for roof venting to be successful, it must be airtight. Venting will work together with roof insulation to promote energy-efficiency and save a home or business owner money. When insulation is installed properly, it will not require any future maintenance and will also function permanently in a structure.
The purpose of roof insulation is to resist heat flow.
Roof insulation is rated with an R value; the higher the R value, the more heat flow resistance the insulation provides. When purchasing insulation for a roof, you should shop according to desired R value as a top priority.
Basic tips for installing insulation include:
- Take care not to block soffit vents with insulation.
- Leave a 3 inch clearance around fixtures that produce heat, like ceiling lights.
- Wear long-sleeved clothing and safety gear to prevent skin irritation.
- Wear a mask to prevent insulation particle inhalation.
One primary purpose of roof insulation is to prevent the formation of ice dams, as mentioned above. Ice dams most often occur after heat enters an attic of a building and causes snow to melt on the roof. Melted snow will accumulate and re-freeze on roof edges to create a heavy ice dam.
If ice dams aren’t removed promptly, more water may collect throughout a cold or wet season. This moisture will corrupt shingles and can spill over the edge of a roof to form potentially dangerous icicles. A simple ice dam may wreak havoc on a structure to corrode insulation, crack plaster or sheet rock, rot walls, and cause paint to blister.
Roof insulation can be used to prevent an ice dam and keep roofing materials cold by:
- Sealing bypasses.
- Insulating roofing materials.
- Ventilating roof deck.
In short, proper ventilation and insulation work hand-in-hand to support the integrity of a new roof. Insufficient venting can cause moisture to collect on insulation to reduce its effectiveness and potentially damage a structure. Insufficient insulation will leave a roof vulnerable to a number of surface issues, including ice dams, that could damage roofing materials.
You truly can’t have one without the other!
