What Is A Building Envelope?

Your home’s building envelope is all of the exterior elements that maintain a dry, heated, or cooled indoor environment. Building envelope design involves both architectural and engineering practices that draw from all areas of homebuilding. A properly designed, installed, and maintained exterior building envelope will also protect your home from air and water intrusion, mold, and dry rot.

There are three main functions of an exterior building envelope:

• Supporting Dynamic Structural Loads
• Controlling the Flow of Rain, Air, Heat, and Vapor
• Meeting the Desired Aesthetics

Control of rain is fundamental, and there are numerous strategies to this end—specifically, barriers, drain screens, and water storage systems.

Flat And Pitched Roofs

The primary purpose of a roof is to resist water. Two popular roof styles are flat and pitched. Flat roofs slope up to 15° and built to withstand standing water. On the other hand, pitched roofs shed water. However, they do not resist standing water—which can occur during wind-driven rain or water accumulation and ice damming in gutters. Typically, residential pitched roofs have an underlayment material beneath the roof covering as the second line of defense against the elements. Residential roof construction is also vented to remove moisture.

Walls And Exterior Siding

Walls are not as prone to leaks as roofs but can still leak water if they are not designed or constructed properly. In the Pacific Northwest, larger eves and drip edges prevent water from directly hitting or dripping on to exterior wall siding. Unfortunately, we see many multi-story new homes, without drip edges and eves that extend far enough out from the walls to protect the home’s siding. In our opinion, this is a construction defect due to poor design, where performance gave way to an aesthetically pleasing exterior.

Types of wall systems regarding water penetration are the barrier, drainage, and surface-sealed walls. a Barrier wall allows water to absorb but not penetrate. A drainage wall allows water that leaks into the wall to drain out. Ventilation used to aid drying by using a rainscreen or pressure equalization wall system. Sealed-surface walls do not allow any water to penetrate the siding materials. Most materials won’t remain sealed over the long-term, and this system is minimal. Conventional residential construction treats walls as sealed-surface systems relying on the siding and an underlayment layer. We prefer Dupont Tyvek Products.

Control of airflow is essential to ensure indoor air quality, control energy consumption, avoid condensation (and ensure durability), and provide comfort. Control of air movement includes flowing through the air barrier system or through components of the building envelope itself and into and out of the interior space (which can affect building insulation performance significantly). These are air movements within a wall or ceiling that may result in up to 20% heat loss.

The physical components of your home’s exterior envelope include the foundation, roof, walls, doors, and windows. The dimensions, performance, compatibility of materials, and installation process are the main factors that determine the effectiveness and durability of your home’s enclosure system.

Standard measures of the effectiveness of a building envelope include physical protection from weather and climate, indoor air quality, durability, and energy efficiency. All building enclosure systems must consist of a solid structure, a well-designed drainage plane, an effective air barrier, and may include a vapor or thermal barrier. Moisture control is essential in any climate, but the Pacific Northwest presents homeowners with unique challenges because of our cold, wet winters and our hot, dry summers. Our weather, which is perfect for growing Pinot Noir grapes, is not ideal for exterior building envelopes. Modern building technology continues to evolve and has caught up to the weather, however. We are now building some of the most energy-efficient, eco-friendly homes on the market, right here in Portland.

At SFW Construction, we currently don’t build new homes. However, we are involved in every aspect of the exterior building envelope. We specialize in all aspects of the exterior building envelope, which makes us a perfect fit for when you need something repaired. Our experts repair problem areas and integrate new materials providing better than new solutions.

Often, we will go on-site to fix a roof only to find out that water has been leaking for some time, and there is dry rot underneath. The process of fixing the dry rot will mean we will need to perform a target repair to that area of the exterior building envelope. If that same leak has compromised the siding, we are able to tackle that too, find out what caused it, and provide a solution that is as good, if not better than when the house was new.

If your home’s building envelope is compromised in any way, please contact us for a FREE “no obligation” Consultation.