The Art of Building: Part 2 - Envelope & Systems
A new home under construction, architecture by mwworks (photos: Jill Hardy).
At long last, we are pleased to continue our “The Art of Building” series. In Part 1, the early construction milestones in the building process were explored through a visual tour of a Seattle home. Beginning at the foundation, we walked through the framing, the sheathing, and topped out at the roof.
Now that the basics are in place, we are shifting focus to the envelope and systems. These hidden components keep our homes dry, our loved ones warm, and distribute the fresh air that we breathe. Read on to learn about the crucial elements that lead to a healthy and comfortable home.
Building Envelope
What is a building envelope, what does it mean for a building to breathe, and why does it matter?
The building envelope comprises all components that create a barrier between the interior, conditioned space and the outdoor, unconditioned environment. Foundation, roof, walls, doors, and windows all play a part in sealing a home. Regulating the temperature of a home is resource intensive and is a significant expense on the homeowner. Air leakage through the building envelope contributes to high heating and cooling costs. A continuous, unbroken, durable barrier keeps rain from entering the home and keeps energy and maintenance costs down.
Prosoco’s air/water barrier applied to walls and FastFlash liquid flashing system applied around openings.
Water Proofing
As air circulates through our homes, water can also penetrate the walls in the form of water vapor. If this water is trapped inside the building by an impermeable vapor barrier, it results in mold and unhealthy air quality. A “vapor permeable” system keeps liquid (rain) out while allowing water to escape. When selecting an air and water barrier, it is important to choose a product with safe chemical ingredients that will not ‘off-gas’ and release chemicals into the air over time. Prosoco, a building envelope manufacturer producing liquid vapor barriers, uses no “red list” materials while allowing the building to breathe.
Windows ready to be set in place.
Window Detailing
Before windows are installed, a certain amount of preparation is required. A waterproofing consultant can review the architect’s drawings to ensure that every transition and detail is properly sealed. Before rough openings can receive doors and windows, they need to be treated with flashing. Flashing is a thin, impervious material that prevents liquid from passing through building joints. The featured home uses a liquid flashing system made by Prosoco (FastFlash) that has been applied to window openings for waterproofing. Once the windows and doors are in place, the house achieves ‘dry-in’ status and the installation of weather-sensitive materials can safely begin.
Roughing-in Mechanical, Electrical, & Plumbing (MEP)
Roughing-in refers to the initial installation of mechanical, electrical, and plumbing services in a building. These systems silently power our homes like a well-oiled machine, concealed within the walls and ceilings. The visible components that we interface with daily, like faucets and light fixtures, will not be installed until drywall is in place and the MEP finishing phase occurs.
MEP services concealed in the walls and ceiling.
Mechanical
HVAC stands for Heating, Ventilation, and Air Conditioning. Modern technology presents us with numerous ways to achieve acceptable indoor air quality and thermal comfort and a mechanical engineer will work with the architect to determine the appropriate system for a homeowner’s needs. Thoughtfully locating the building in the landscape will capitalize on the existing conditions of a site, such as shade from a nearby tree or ventilation from a passing breeze. Intentionally placing openings based on solar orientation and shading sun-struck windows with screens or awnings will passively reduce heat gain in a building. Passive HVAC systems such as natural ventilation or the use of thermal mass to control temperatures can reduce the energy needed to heat and cool a home.
Electrical
When roughing-in the electrical systems, an electrician pulls cables through wood framing and inserts these into walls and ceiling power boxes. It is equally important to utilize passive systems when designing the lighting in a home. Clerestory windows, or windows placed above eye level, as well as skylights can admit light into a room while maintaining privacy. Natural light is beneficial in that it helps to regulate our circadian rhythm and reduces the need for artificial lighting.
Plumbing
During the rough-in plumbing phase a plumber will route pipes through wall cavities, penetrate drain and water supply lines through floors, attach waste lines to the necessary sewer or septic systems, and connect the plumbing system to the main water supply. No fixtures or end elements will be installed during this phase.
Finishing
Insulation fills the wall and ceiling cavities.
Insulation
Filling wall cavities with insulation does not just regulate temperature and conserve warmth, it also effectively reduces sound transmission from room to room. Wool insulation is a non-toxic, natural material that has a lower embodied carbon than two common artificial insulation products, extruded polystyrene and polyisocyanurate. This means that less greenhouse gas was released throughout the process of creating the material and transporting it to the site. An added benefit of wool insulation stems from the natural properties of wool itself. It manages moisture naturally and improves the indoor air quality of a home by absorbing harmful chemicals.
Drywall hung and ready to receive final fixtures.
Drywall
The building envelope is not complete until the drywall is in place. Now that the cavities have been filled and the systems are in place, the walls can be sealed. Drywall is the final step in a wall assembly.
Stay tuned for The Art of Building: Part 3¸where we will discuss the many ways a building comes to life through rich finish materials, artisanal metal and woodwork, and site work. Let the finishing process begin!