How do you know if your roof is properly vented?

Some deck builders install blocking throughout the frame to increase the strength of long joist spans and promote a more solid structure. Often times, scrap materials from your framing lumber may be used for blocking.
For every 150 square feet (sq. ft.) of attic space, 1 square foot of ventilation is recommended.

The general advice we give is that you should always insulate between and above the rafters (warm roof) or between and under the rafters (cold roof).
Without them it is actually easier to insulate your attic, because you do not have to worry about covering up the vents or installing rafter baffles to ensure the vents breathe.

A poorly or improperly ventilated attic can cause early degradation of your roof. Moisture accumulation in the attic can cause nails, flashing, and duct straps to rust, resulting in damaging leaks. Excessive moisture can also allow for the growth of mold and mildew beneath your shingles, causing them to rot.
Blocking required every 4′ – 6′. Blocking must be equally spaced in rows, maximum of 4 to 6 feet apart. WHY IS BLOCKING NEEDED? Solid wood blocking will help reduce up or down movement and/or twisting of joists.

Rafter vents come in 4-foot lengths and 14-1/2 and 22-1/2 inch widths for different rafter spacings. Rafter vents should be placed on your attic ceiling in between the rafters at the point where your attic ceiling meets your attic floor.

It is ok to have more intake than exhaust. You should only have one type of exhaust ventilation on your roof. There are several types to choose from. There are power attic vents, Roof Louvers, wind turbines, gable vents, and ridge vents.

Dangers of Too Much Ventilation
The two main dangers associated with too much ventilation involve roof damage and increased utility bills. If you have too much air circulating, your roof will collect moisture causing damages that will weaken spots and then cause leaking.

We recommend spacing baffles 18 inches to two feet apart. Secondly, baffle depth does matter! You need to hit the minimum depth of 12 inches or more to make them effective. Sound can pass through baffles, hit the ceiling, and come back down causing discrete reflections.
You can’t have too much soffit venting, but it’s worth noting the minimum requirements. Usually, 4-in. by 16-in. soffit vents are rated for 26 sq.

All plumbing systems require at least one vent stack. It is designed to vent all the gases that accumulate inside the system through the roof into the atmosphere, and helps maintain the trap seals of each fixture.

A non-ventilated roof can also cause extremely hot attics, where the heat builds up and eventually causes damage to the wood framing, rafters, underlayment and more. Ensuring your roof is evenly and properly ventilated helps that air to escape and extends the lifetime of your roofing system.

How Many Vents Do I Need? The general rule of thumb in these situations is of roughly one vent per every 300 square feet of attic area if the attic has a vapor barrier. If not, there should be one vent for every 150 square feet. You will need to have 1 square foot of vent area for every 150 square feet of attic space.
Keep in mind not all rafter need baffles, just those with intake vents at the soffit. If you don’t have baffles installed, check your intake vents for any type of blockage for insulation or debris. This can be cumbersome since you will need to squeeze to the corners of your attic.

Exhaust vents should always be placed at the highest possible point on the roof (at or near the ridge) which typically aligns with the highest part of the attic space.

When the rafters are exposed, such as in timber-frame houses, this technique is not feasible. The basic approach to insulating a roof with exposed rafters involves placing insulation on the exterior side of the finish ceiling and covering the insulation with a layer of sheathing.

But how many roof vents does one home really need? A general guideline is homeowners need one square foot of roof vent for every 300 square feet of ceiling space, if your home has a roof with a vapor barrier, or 1:300. If not, you should have one square foot of roof vent for every 150 square feet, or 1:150.
Rafter blocking is an essential part of the roof framing process in that the blocks provide a stop for ceiling insulation and a continuous surface for the roof sheathing to be edge nailed to.

Divide the square footage by 150 to calculate the area of ventilation needed, since you need 1 square foot of vent space for each 150 square feet of attic space. This ratio is required for modern insulated homes. If you have 3,000 square feet of attic space, this equates to 20 square feet of ventilation needed.

If the kitchen and living room are not separate, at least three vents of the same EA as for habitable rooms should be provided in that space. The total number of vents in habitable rooms and kitchen should be at least 5, or 4 if a one bedroom property.
They say that poor or non-existent ventilation might cause attic temperatures to rise to 150 degrees or higher in the summer. That can lead to damaged shingles and other roofing materials as well as a buildup of condensation and development of mildew and mold.

Generally, the size of your home determines how many vents you will need per room. If your room is larger than 100 square feet, you will need more than one vent (at least two) to really get adequate airflow to the room. If the room is smaller, you only need one.