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What Is a Building Shell/Envelope and Why Is It Important?

by vscontent on January 12, 2018


Building Shell Envelope

Your house may be stationary, but it’s not stationery. So what does an envelope have to do with your home? What is a building envelope (aka shell)? Much like an actual shell or envelope, your building’s “shell” is everything that separates the inside from the outside.

The building shell/envelope comprises:

  • Floors
  • Walls
  • Doors/Windows (Fenestrations)
  • Roof

Without a building shell or envelope, you wouldn’t be living in a home at all. It’s the thing that protects you from the elements, allowing a safe, dry, and comfortable indoor habitat.

Why is a building shell important?

The building shell is important for keeping the elements out and conditioned air inside. Newer buildings utilize more energy efficient technology and design to save money and energy from air leaks. The shell is crucial for indoor climate control.

In addition to separating conditioned air from unconditioned air, the envelope/shell also protects the home from water and moisture, provides support, and plays a big role in the home’s look and feel.

But back in log home days, air came in and out through gaps in the envelope. Therefore, nobody needed to worry about mechanical ventilation.

As building envelopes became stronger and more resilient to outside forces, more and more air ends up trapped inside. While this is a good thing for energy efficiency, breathing the same stale air over and over again has many negative health effects.

Allowing some air to ventilate the home is a good thing. That’s why every home should have balanced ventilation.

Do I have enough ventilation?

The building shell is more important during the cold winter months. Due to increased insulation (door sweeps, weatherstripping, storm windows, and caulking), homes in the wintertime are more prone to the negative effects of poor ventilation.

Last week we discussed the different types of ventilation systems and why a balanced mechanical system with heat recovery ventilators are the best way to improve indoor air quality while minimizing the associated energy loss.

The blower door test

A professional blower door test is often a part of an energy audit. A professional will seal off your home and pull air out of your home with a powerful fan. The negative pressure inside the home will cause outdoor air to flow into all of the gaps and cracks in your home. This is how the professional energy auditor can pinpoint all of the air leaks in your building’s shell.

A professional blower door test gauges the air tightness of your home. It’s a good idea to test a building shell’s integrity in order to:

  • Reduce energy waste
  • Prevent moisture and humidity problems
  • Increase comfort levels by getting rid of drafts
  • Determine how much insulation and ventilation you need

Contact Pacific Heating & Cooling for your home energy evaluation. Our team of professionals can tell you if your building envelope is doing its job or not.

Why is ventilation so important?

In the past, when homes were a lot draftier and less efficient, there wasn’t much of a need for mechanical ventilation, since air was constantly being refreshed through all the cracks and gaps in the building’s shell/envelope.

Now that homes are more airtight and insulated, air effectively gets trapped inside with nowhere to go.

Additionally, the building materials of yore were all-natural. Now, many building products (such as particle board and plywood) result in a significant amount of offgassing. Offgassing emits volatile organic compounds (VOCs), formaldehyde, and other chemicals that can be dangerous in both the short and long-term.

Effects of inadequate ventilation:

  • Offgassing (from household cleaners, air fresheners, nail polish remover, printers/photocopiers, plywood and other building materials)
  • Humidity (which leads to mold, mildew, and fungi)
  • Viruses, Bacteria, Dust, Dander, and Debris
  • Carbon Monoxide and Other Gases

If you are feeling sick in your home, speak with a medical specialist and your local HVAC professional. They can help you ventilate and filter/clean your air.

In addition to air filtration, cleaning, and ventilation, be careful about what you bring into your home in the first place.

Once you know more about your home’s shell, you can find ways to improve it. Remember, if you ever make major shell improvements, contact a professional HVAC technician to determine if you have the proper amount of ventilation.

Learn more about indoor air quality solutions here.

Contact Pacific Air Systems Heating & Cooling for professional home energy evaluations and indoor air quality solutions. Reach us 24/7 at (253) 292-3995!

Since 1984, we’ve been proudly serving our communities in Federal Way, Graham, Spanaway, University Place, Steilacoom, Sumner, Lakewood, Puyallup, Tacoma and Gig Harbor.

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