Attic Ventilation: Renaissance Project House - Part 9

Описание: Renaissance House Playlist:
   • Renaissance Project House  
This will be updated as segments are added.

Soffit, Fascia & Trim Defined – Rafters are the parallel beams that support the roof above the top floor of the house. Fascia is the vertical board that closes off the end of the rafter tails. It’s normally vertical, sometimes sloped. The Soffit is the horizontal under-hang that completes the boxing-in of the rafters and the sheathing. That box is known as the “eaves” or the “overhang” of the house. Lookouts are short pieces of 2x4s that horizontally connect the rafter tails to the top of the wall. A Closed Soffit is a closed box. An Open Soffit leaves the rafter tails exposed. “Trim” is a term used to describe soffit & fascia.

Attic Ventilation Defined - Moisture is the #1 concern. Heat is #2.
We’ve gotten much better over the years at building houses that are energy-efficient. We’re better at building “tight” Homes - that means they’re designed to keep the elements outside & your energy dollars inside. But that level of homebuilding expertise can also cause some problems. Modern insulation and house-wrapping techniques create a tightly sealed envelope that blocks leaks, drafts and other unintentional paths for fresh air to enter a house. Those techniques also prevent “stale air” inside the house from finding a path to exit.

A “Sick House” Defined– Insulation and house-wrapping create a “stale air” environment inside. The air gets stale because the same air keeps getting conditioned – you notice it inside an airplane cabin sometimes. Lots of moisture gets produced in a home (showers, boiling water, people & pets breathing, condensation when the weather changes, etc) & it floats up into the attic as water vapor in rising air.

One of the biggest problems is managing the moisture. If we don’t control that moisture, we can do a lot of damage to the materials that we build into your new house. A buildup of moisture will promote the growth of mold, mildew & other biological pollutants. Moisture over time will rot the wood in the frame of your house and remove all strength from that wood. Once the frame of your house is ruined, the entire investment you’ve made in your new house is ruined along with it.

If it’s not vented away, mold can grow in the attic, decreasing the indoor air quality and making your house “sick”. Warm air naturally rises, so it wants to pool inside the attic. If the attic is hot and improperly vented, then energy bills go up because that hot air pocket grows and works its way down into the living area. The HVAC cannot work efficiently, and you have to pay to cool that hot air out of the attic. The combination of excessive moisture & heat can make your roof shingles deteriorate & fail prematurely. Proper venting is by far the most cost-effective way to cool the attic.

Attic Ventilation Designed - The best venting design puts vents in the soffit (for intake) and up near the ridge line (for exhaust). That way, fresh air naturally bathes the attic as hot air rises up & out of the ridge line and fresh air replaces that outgoing air through the soffit vents.

Soffits will have either discrete or continuous vents. Many builders install individual 4x16 or 8x16 vents, or else they create a continuous soffit vent with screen door material all the way around the eaves.

Even with great tight houses, there could be too many places between a ceiling & an attic where air can leak. Some tests show that air exfiltration (that’s air that leaks out of a house – the opposite of infiltration) could be severe when powered fans suck air out of an attic.

Different styles of passive roof vents
Michael showed a Passive Turbine Vent, a common roof vent. Most people call it a “twirler”. It’s circular, and it twirls when the wind blows through it – that twirling helps draw hot air out of the attic, which draws cooler air in through the soffit vents to clean out the hot air in the attic. It works best when it’s mounted high on the roofline.

Sometimes people like to put plastic bags over these twirlers in the wintertime to prevent cold air from moving through your attic and into the living area. This can cause problems because you end up with a lot of moisture buildup in your attic in the wintertime. In cold weather, your house is hot and the air upstairs in the attic is cold, so moisture forms just like it would on the side of a glass of ice water in the summertime. So, leave those twirlers open & exposed, even in the wintertime.

MORE FROM YOUR NEW HOUSE
Featured videos:
   • YNH Featured Videos  

Great DIY Projects from Your New House:
   • DIY - Do It Yourself with Your New House  

Quick Tips - easy tips to make your projects (and life) better:
   • Quick Tips - Great, yet simple ideas for Y...