4 FM quick reads on Windows
1. How To Know Whether To Repair or Replace Windows
Today's tip is about things to consider when trying to figure out whether you need new windows.
Ask yourself if the existing window system is structurally adequate and does it accommodate building movements and structural loadings? If not, it's probably time for a replacement. Also, is the system effective at controlling water leakage and moisture migration? Is the system effective in resisting unwanted air infiltration and condensation? If no is the answer to either of those, start doing some window shopping.
Determine whether a discovered problem is occurring in more than one window. If the problem isn't widespread, it may be possible to address problems on a window-by-window basis. Similarly, find out if any problems might actually be with the adjacent wall system, and not really the window at all.
In general, if the condition of the windows or the peripheral elements like the frame, sash, glazing, hardware, weather stripping, sealants, and exterior paint or other surface coatings are deteriorating, replacement will be necessary. If you're thinking about repairs, make sure to get a good estimate and determine if the cost of repairs approaches the cost of replacement. If it does, then replacement makes much more sense than repairs.
2. To Repair or Replace Windows
Today’s tip is about what to consider when trying to decide whether to repair or to replace windows.
When trying to decide whether to repair or replace, consider these seven questions:
1. Is the existing window system, including connections, structurally adequate and does it accommodate building movements and structural loadings? This is critical from a safety as well as a performance standpoint.
2. Is the system effective at controlling water leakage and moisture migration?
3. Is the system effective in resisting unwanted air infiltration and condensation?
4. What is the condition of the system components? Check the frame, sash, glazing, hardware, weather stripping, sealants, and exterior paint or other surface coatings.
5. Are problems widespread or isolated? It may be possible to address problems on a window-by-window basis.
6. Is it possible that the adjacent wall system is contributing to the problems experienced?
7. Is the building historically significant?
In general, if the following conditions exist, replacement is probably preferable to repair. One: Is there excessive deterioration of the window system? Two: Is the effectiveness of the repairs questionable? Three: Would the cost of repairs approach the cost of replacement, or does the life-cycle cost of replacement prove cost-effective passed on lower energy and maintenance costs. Four: Is it impossible to do ongoing maintenance practically after repairs are made?
Deciding whether to repair or replace isn’t any easy decision, but making the right decision based on careful assessment of existing conditions can help save money in the long run.
3. How to Measure Exterior Efficiency
Today’s tip is about how to measure the efficiency of certain exterior elements. For new construction, the ASHRAE 90.1 standard is the baseline for measuring how efficient a building is. But there are several metrics for exterior building elements that can show how they contribute to, or are detrimental to, energy efficiency goals.
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 roofs, the two main measures are solar reflectance and infrared emittance. Solar reflectance, also known as albedo, measures a surface’s ability to reflect infrared, visible and UV light from the sun. 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.
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.
4. How to Design Windows and Openings for Efficiency
Today’s tip is about how to think about windows in terms of energy efficiency. The first and most important thing facility executives should consider in existing buildings is upgrading old, leaky windows to new windows. This alone could result in huge energy savings. Considerations when selecting new windows that affect window performance include frame and spacer material, number of panes, gas between the panes, glazing emissivity and transition to the solid wall.
In new construction, facility executives should specify high-efficiency windows and glazing, and make sure that window openings are properly placed so that solar load is reduced. But facility executives should also consider how window openings can take advantage of natural daylight so that lighting energy can be reduced. Use an energy modeling program, or even Building Information Modeling, to determine where the happy medium is between solar gain from large expanses of glass and enough natural daylight to keep occupants happy and reduce lighting loads.