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Building Envelope

The envelope of your building is critical to the functioning of your other building energy systems. When considering energy capital improvements, many people overlook this "system" other than their windows. Wall and roof insulation, assembly, penetrations, openings - including windows – all act as a barrier between your conditioned space and the outside world. Here in Pennsylvania we have a temperate climate, which actually means we have two extremes - cold in winter, hot and humid in summer. The envelope needs to work for both of these.

Where to begin? As you work to tighten up your building envelope, we highly recommend you begin with the Building Operator Certification training on energy efficient building and operational maintenance practices. Additionally, for those facilities who have already instituted energy efficiency measures, Building Re-Tuning training is a systematic process to identify and correct building operation problems that lead to energy waste. Both of these programs outline the steps needed to better manage your building. For more information go to: link to the BOC Main Landing Page.

Where can I start now? If your building has water leaks, this is the first thing you must address. Water leakage will damage insulation and often is a source of air leakage. If you can afford to do so, hire an energy auditor to conduct an energy audit of your building envelope; every building is different and their experience across building types makes it faster and easier for them to find air leaving and entering your space. If you cannot afford an auditor, ask employees where they feel a breeze, look for cobwebs, or invest in a low-cost smoke pencil. Sealing air leakage at assembly joints, around doors and windows, and at penetrations into or through wall cavities such as wiring or conduit runs are important steps. All of those small gaps can quickly add up to a large opening. Bonus! Your Fire Marshall will be happier about sealed penetrations.

What about your walls? Examine your insulation in both your walls and roof. If you have a large building or number of buildings, an infrared (IR) camera can be very beneficial. An IR camera measures the intensity of infrared radiation (radiant energy) being emitted by the surface it is viewing, not the surface temperature. You can use an IR thermometer in conjunction with your camera to help understand the images. The images can clearly show where you have slumped (or no) insulation, places behind trim where insulation or sealant is missing around doors or windows, and help identify where ductwork may be brining cold or hot air along with conditioned air into your occupied space. It is best to use these cameras on cloudy, non-windy days when the temperature difference between conditioned and outside spaces is more than 20 degrees F. Insulation levels in building codes (the R-value) should be treated as a starting point. Additional insulation can be beneficial, especially if your building was not built to the current code. Even though PA has not yet adopted the International Energy Conservation Code for 2015, we recommend you look to the recommended insulation levels in that code. PA spans Climate Zones 4, 5 and 6.

Aren't my windows a problem? Not always. That's why we have you start with the steps above. But, yes, your windows and doors provide light and egress, and often that includes egress for your conditioned air! Ensuring doors and windows close fully and are properly sealed – both the unit itself and to the wall where it is attached and is critically important. Visible light around the edges means significant air loss, and thus financial loss. Double and triple paned windows with low-e glass and a proper u-value can make a lot of difference, as can adding a second door to create a vestibule. Again, take a look at the recommended values in the IECC mentioned above.

What about using – or blocking - the heat from the sun? With our temperature swings in Pennsylvania, there has been some confusion about the use of high-albedo (high reflectivity) surfaces such as white roofing or light-painted walls. Most commercial buildings need more cooling than heating, so absorption during the winter months thanks to high-mass concrete or other masonry or dark surfaces is less necessary in most situations. As with most buildings, every need varies, so take that into consideration when looking to replace your roof or paint your walls. The use of sun shading – deep overhangs that block radiant sun in the summer but allow winter sun in through the windows to heat up the space or a large thermal mass – can be one method to manage your building's design to your energy advantage. Some owners find combining overhangs, a light roof to repel summer sun and darker walls to absorb winter sun, to be a good compromise for these temperature swings. Also consider blocking reflected heat from nearby buildings or parking lots as those thermal masses create heat islands that raise local ambient air temperatures and can significantly contribute to your energy usage. Mitigate this with deciduous plantings - an affordable and attractive solution.

Want to do a deep analysis of your building envelope and other systems? If you are able, you can rate your building envelope in the free, online Energy Asset Score tool from US DOE. This tool examines all of your building systems and helps identify which ones need an upgrade soonest.

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