Controlling Humidity in an Attic with Spray Foam Insulation
网页2021年7月29日 — The building code doesn’t require any conditioning of the air in a spray foam attic. For roof lines insulated with air-permeable insulation (“the fluffy stuff”— fiberglass, cellulose, rockwool), the International Residential Code (IRC) requires 50 cfm of supply air per 1000 sq. ft. of attic floor area with a vapor diffusion port.
Does Spray Foam in the Attic Make It a High-Performance Home?
网页2021年5月27日 — Increase airtightness from <5 ACH50 to <3 ACH50. Install whole-house mechanical ventilation that’s not exhaust-only. Cover the rafters with a minimum of R-3 insulation. This amendment would make it a prescriptive requirement to put R-20 spray foam insulation on the underside of the roof deck. That’s the easiest way to pass code.
Creating a Conditioned Attic - GreenBuildingAdvisor
网页2010年12月31日 — You can probably combine rigid foam and spray foam safely, as you propose -- but note that exposed spray foam is a fire hazard. Most code inspectors will require the spray foam to be protected on the interior with a so-called "thermal barrier" like drywall. More information here: "Thermal Barriers and Ignition Barriers for Spray Foam."
High Humidity in Unvented Conditioned Attics
网页2016年8月26日 — At 140 F, 80% humidity corresponds to 120 torr, or 16% of atmospheric pressure. If the attic is at 80 F and 80% humidity, that's about a 21 torr vapor pressure of water. So compared to that hot humid attic, the vapor pressure at the other side of the foam is a factor of six higher.
Spray Foam Insulated Homes Need Ventilation
网页2014年10月22日 — Most installations of spray foam insulation, when properly installed, act as an air barrier. When you use it instead of the fluffy stuff (fiberglass, cellulose, cotton), a house will be more airtight. That's good. When a house is airtight, the nasties in the indoor air tend to stick around. Volatile organic compounds (VOCs), water vapor, odors, radon, and other stuff you don't want to immerse ...
Spray foam against underside of roof deck? Or install vent baffles ...
网页2019年7月10日 — By simple averages and 24" rafter spacing, 8" of closed cell spray foam and 2x10 rafters you get about R33 for the assembly, about R32 with 16" rafter spacing. The thermal bridging does make a big difference in the performance of the overall assembly. No, escaping heat is energy loss, but it won't damage your roof.
High Humidity in Spray Foam Attics - GreenBuildingAdvisor
网页2016年10月26日 — When the water vapor exits the spray foam, it increases the relative humidity of the layer of air near the foam. Because water vapor is lighter than dry air (mostly nitrogen and oxygen), that layer of air can move upward in the attic. The result is higher humidity at the ridge than at the floor. Lstiburek calls this the ping-pong effect.
Thermal Barriers and Ignition Barriers for Spray Foam
网页2014年4月11日 — Exposed spray foam can be hazardous. According to a guide for spray foam installers, “Thermal Barriers and Ignition Barriers for the Spray Polyurethane Foam Industry,” “When exposed to fire sources, such as trash fires, welding arcs, cutting torches, or red-hot metal, unprotected SPF [spray polyurethane foam] can ignite and may result in ...
80% efficiency furnace in a foamed / sealed attic space
网页2018年10月15日 — We are planning to replace the furnace in a year or two. The furnace is an American Standard Silver 80 100,000 BTU. From the manual and ANSI Z223.1 the furnace is a class 1 fan assisted combustion device. From ANSI Z223.1 9.3.2.1 with an unknown ACH (I assume ACH50, but the standard copy I have doesn’t clarify), you …
Spray foam & sealing off soffits from attic - GreenBuildingAdvisor
网页2017年2月4日 — I had a spray foam contractor to my house last week to discuss spray foaming the underside of our roof deck. We did everything in renovating our home right except for the ~30 can lights we had put in. I don't notice heat loss as much but the heat gain in the summer is obvious. I've given up trying to insulate and air seal so I want to move the envelope up. I've researched this a bit and know ...