4 FM quick reads on window
1. Testing Window Systems
During a construction project or significant renovation involving windows, the suitability of the selected window system for the facility will have to be verified. The best way to test a window system is to build a functional mockup.
The mockup can be constructed as part of the building or it can be free-standing, but it should contain all the components of the window and wall, including the air and vapor barriers, flashings, caulking, and the exterior finishes. Testing the mockup is critical when working with dissimilar materials.
It's important for the mockup to be built in the correct sequence by the subcontractor who will be performing the actual work on the job to ensure the mockup is built correctly and the same way it will be done on the building. In addition, the construction manager, architect, subcontractor, suppliers, owner and third-party consultants should all be a part of building and testing the mockup.
Testing the Window A third-party consultant should be hired to perform the investigation. Essentially, this consultant's job is to test the window system to the point of failure, using the kind of natural elements it will face in the real world — like extreme wind and water pressure from rain. This will detect the weak point in the window system.
There are many different ways to test the window — air vapor testing, smoke testing and water testing among them. A consultant is typically hired to perform one of these various kinds of tests. If the window fails, it may be tested a different way to identify the specific weakness.
A window system will typically fail in one of three ways:
- The materials specified for the window are not compatible with each other.
- The sequence in which the materials are put together to create the window system is wrong.
- There are issues with the window itself from the manufacturer.
2. What Metrics to Look at For Exterior Energy Efficiency
Today's tip is about the important measures facility managers should be aware of when trying to quantify the quality and energy efficiency of exterior building elements. For new construction, the ASHRAE 90.1 standard is the baseline for measuring how efficient a building is. Soon, though, ASHRAE 189.1, a new green building construction code, and the ICC's International Green Construction Code, will be the standards. These standards reference several metrics for exterior building elements that exterior components must meet when choosing the prescriptive path to compliance.
For roofs, the two main measures are solar reflectance and infrared emittance. Solar reflectance measures a surface's ability to reflect infrared, visible and UV light. Generally, the higher the solar reflectance, the more energy efficient the roof will be. Infrared emittance measures a surface's ability to re-emit any energy absorbed back into the atmosphere. A so-called "cool roof" generally has an emittance value higher than .90 and a reflectance value of .65 or higher. Finally, solar reflectance index, or SRI, is a combination of the two via a standard calculation. SRI is the new standard used in LEED.
For windows and skylights assemblies, U-factor measures heat loss. The lower the number, the better the performance. Solar Heat Gain Coefficient measures how well a product limits radiant heat gain from sunlight. Visible Transmittance measures how much light, but not heat comes through. The higher the number, the more light is transmitted. Finally, Condensation Resistance indicates a product's ability to resist the formation of condensation on interior surfaces. The higher the rating, the better.
For wall assemblies, the best measure for efficiency is R-value - or the thermal flow resistance. The higher the R-value, the better the insulating effectiveness. When calculating the R-value of a wall assembly, the R-values of the wall, insulation and any other layers are totaled to arrive at the R-value of the total assembly.
3. Look Out for Window Problems
Today's tip is about understanding how to care for windows and address problems that could turn into huge headaches if left unchecked.
Clearly, the easiest way to avoid letting hidden problems fester and get the longest life possible out of windows is to do regular inspections and complete routine preventive maintenance. Of course, in large facilities, the sheer number of windows makes regular inspections difficult, so experts suggest inspecting several samples on each façade of the building. If you recognize a pattern of problems, it's a safe assumption that most or all of the windows have the same problem.
To complete a meaningful inspection, look at the frames and make sure there is no gap between frame and wall that may have resulted from temperature swings that cause regular expansion and contraction. On the exterior, examine the caulking between the window and exterior wall to make sure it's not cracked and that the seal is still true.
If windows are operable, open and close them several times and listen for groans or other odd noises, which are indications that the windows are out of form. Make sure the operator mechanisms themselves aren't warped or rusty.
Finally, take a good look at the cosmetic condition of the interior and exterior window frames - if the paint is peeling or the wood warping, it's a good sign that moisture is present, where there's moisture, there's probably air leakage too.
4. Reducing HVAC First Costs and Operating Costs
Today's tip concerns saving money on HVAC costs.
The time to start thinking about HVAC is at the very start of programming a new building. That's because life-cycle HVAC costs for a new building are often locked in before the efficiency of chillers and boilers has even come up for discussion.
The siting of the building, for example, will affect solar gain. The choice of windows can influence both heat transfer and solar gain. Likewise, the level of insulation in the walls and roof plays a significant role in determining the operating cost of the HVAC system. And the type of lighting system used in the facility will have some effect on heating and cooling loads.
It's not just energy costs that can be saved. Smaller loads translate into smaller chillers, fans and boilers, reducing first costs as well as operating costs.
Specifying efficient HVAC equipment is important, of course, but by the time talk turns to manufacturers and model numbers, many of the most important decisions regarding HVAC efficiency have already been made. That's why it's useful for facility managers to get involved as early as possible in programming.
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