Photo: Skylar Kang

Can you have too many soffit vents?

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.

finehomebuilding.com - Adequate Roof Venting - Fine Homebuilding

What is the cheapest way to heat a shed?

While water-based underfloor heating systems are available, electric underfloor heating systems are often better for sheds. Halogen heaters – An...

Last updated Nov 26, 2022

Does adding more cement make concrete stronger?

You can add more Portland cement to bagged concrete to make it stronger. You can also add hydrated lime. To make the strongest concrete, the sand...

Last updated Jun 6, 2019

Can I build my own shed?

Yes, with the right plans you can build your dream shed.

Learn More »

Promotion

Q:

I am having the shingles replaced on the roof of my ranch-style house. The roofer is concerned about attic ventilation and recommends installing a ridge vent and closing off the existing gable vents. He also says that the rectangular metal soffit vents may not be adequate and recommends installing more to eliminate the risk of the roof sheathing rotting. There are five vents in each soffit, and they measure about 4 in. by 16 in. each. Is it necessary to close off the gable vents? If so, how can I do that? Do I have to remove them and fill in the void with siding?

And how do I know how many soffit vents to install?

Mark Villar, Middletown, CT

A:

Editorial Adviser Mike Guertin replies: If the roof sheathing hasn’t begun to rot already, it’s unlikely that replacing the roof shingles will cause it to occur. Still, it’s a good idea to address ventilation to reduce attic heat in the summer and to reduce the chance for ice dams in the winter. Most likely, the roofer is recommending closing off the gable vents when adding a ridge vent to prevent short-circuiting of the air. When gable vents are left open, air can enter through the gables and bypass the soffit vents. If air flows in through the gables and out the ridge vents, the entire roof doesn’t receive the full effect. The air isn’t entering through the soffit vents, traveling up the underside of the roof, and exiting through the ridge vent. You don’t have to remove the gable vents, though. Just screw a piece of rigid foam or plywood over the vent from the inside. When the siding is replaced, the old gable vents can be removed and the openings filled. The standard equation for older homes that don’t have air barriers and vapor retarders (now required) is 1 sq. ft. of vent area for every 150 sq. ft. of attic floor. If your house is 26 ft. wide by 48 ft. long, you have a 1248-sq.-ft. attic floor and need 8.32 sq. ft. of total vent area. If, however, the attic floor has been air-sealed and has a vapor retarder between the inside of the house and the attic, the equation is 1 sq. ft. of vent area for every 300 sq. ft. of attic floor. Ideally, this 8.32-sq.-ft. total vent area is split: 4.16 sq. ft at the ridge and 4.16 sq. ft. at the soffits. Each type of vent has a range of effective vent area per linear foot—this is called the net free vent area (NFVA). Ridge-vent NFVA ranges from 14 sq. in. to 18 sq. in. per lin. ft. (Check manufacturers’ instructions for the ratings of specific products.) If 46 ft. of ridge vent (often it does not extend to the ends) is installed and the product has an NFVA of 15 sq. in. per lin. ft., we can take 46 ft. and multiply it by 15 sq. in., which equals 690 sq. in. Converted to square feet (690 divided by 144), the total is 4.8 sq. ft. This ridge vent supplies 4.8 sq. ft. of NFVA, which is just over half of 8.32 sq. ft.

What is the cheapest wall covering?

Plywood Plywood If you intend to maximize the cost of wall covering in the cheapest possible way, we recommend you use plywood. They're accessible,...

Last updated Mar 10, 2018

How do you make a shed a livable space?

Top Ways To Turn A Shed Into A living Space Run power to the shed for lights, electronics & HVAC. Choose a way to climate control – Heating &...

Last updated Nov 14, 2021

Promotion

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. in. of NFVA each. With a total of 10 vents, you have a total of 260 sq. in. (1.8 sq. ft.) of soffit-vent area. Since you need at least 4.16 sq. ft. of NFVA, you’ll need to add 14 more of the 4-in. by 16-in. soffit vents (for a total of 4.3 sq. ft. of NFVA in the soffits). If the soffits are wide enough, you can remove the existing vents and replace them with 8-in. by 16-in. vents, which provide 65 sq. in. of NFVA per vent. With 10 of these large vents, you’ll end up with a more adequate 4.5 sq. ft. of NFVA in the soffits.

From Fine Homebuilding #257, pp. 80-81, January 6, 2016

finehomebuilding.com - Adequate Roof Venting - Fine Homebuilding

What is the best material to insulate a shed?

Sheeps Wool insulation slabs can offer both great thermal insulation and regulate air moisture, avoiding dampness within your shed. Breathable...

Last updated Aug 30, 2018

Can I live in my outbuilding?

If the outbuilding is existing, converting it then into primary living accommodation IS allowed. Aug 4, 2022

Last updated Feb 2, 2021

Promotion

Is 2022 a good year to build a home?

Barring any unforeseen calamities, 2022 could be a good year for homebuilders and buyers. However, the effects of inflation, new COVID variants, or...

Last updated Jul 5, 2021

Can I build my own shed?

Yes, with the right plans you can build your dream shed.

Learn More »

Promotion

Why does America not have radiators?

If you're a European walking into the average American home, you'll notice that the walls are conspicuously free of radiators. That's because most...

Last updated Jan 18, 2018