Having energy efficient buildings is acquiring more and more important as energy is a critical economical issue due to unsustainable supplies high demand for it. It has become very important for households to create energy efficient homes that consume less energy and lower the release of harmful gases into the environment. Therefore, building energy-efficient homes is the top objective for homeowners as it can save cost by using lesser energy for utilities as there would be minimal need for running utilities to keep homes cool or warm.
The design of windows plays a critical role in determining the comfort level inside homes. The rate of heat transfer through the windows is a major factor that influences the energy efficiency of homes. From the choice of the window frame material to the type of glass, everything contributes to the level of energy efficiency inside homes. The desire to boost the energy efficiency of homes is a major motivation for homeowners to undertake home improvement projects, including window replacement. It helps to keep homes cool in summer and warm in winter, thereby reducing the use of utilities that brings down energy bills. And not only the window design but also the window treatment and floor coverings help to improve the energy efficiency of homes
To build energy efficient homes, you need to install energy efficient windows that can minimize the use of machines to artificially cool or heat buildings by ensuring proper heat transfer through the windows. Technological advancements have resulted in the development of window designs that can cool or heat homes four times more efficiently than conventional windows. Choosing high-performance windows and installing it across the home can improve the quality of home insulation, which leads to efficient use of energy at low cost.
The energy efficiency of windows – what it means
To know how much energy efficient any window is, you must be familiar with two factors, namely U-value and Solar Heat Gain Coefficient (SHGC). The rate of heat loss from your window is its U-value and expressed as a number ranging between 0.20 and 1.20. Windows that have excellent insulation have lower U-value that also indicates its high resistance to heat flow. SHGC is a measure of the window’s ability to block the heat from the sun measured on a scale of 0 to 1 and lower is the SHGC better is its heat-blocking ability. This feature is especially important for people residing in areas of a hot climate. When selecting windows, pay attention to these factors besides the design and style to ensure comfortable living.
Window components contribute to its energy efficiency
The window performance is the sum of the performance of various components like frame, glass, hardware, etc. that act in unison to provide overall performance. Each of the components is responsible for energy conservation in its own way by controlling the rate of heat loss and heat gain that translates into less energy consumption by the whole building and creates energy efficient homes.
Let us have a closer look at the window components that contribute to the scheme of things to improve the energy efficiency of homes.
Low E-glass is low emissive glass that uses a special coating on the surface to minimize the heat flow across the glass surface without inhibiting the passage of light. The coating is so thin that it remains invisible but performs its duties efficiently that results in lower U-value of the glass which points to how well the glass prevents heat loss or gain from all sources other than the sun. Lower U-value means that the window is highly energy efficient and has superior insulating properties that control the heat transfer rate. Lower e-coating on standard glass is only effective to keep solar radiation under control but does not help to regulate convective and conductive heat flow.
The property of Low-E glass allows it to block only the heat that comes in direct contact with the glass surface and ideal for keeping homes cool on a hot day by reducing the transfer of outside heat to the indoors. Conversely, on cold days, it retains the heat inside homes and keeps it warm and comfortable. Also, low e-glass prevents UV rays from entering homes.
Double glazed windows
Preventing all sorts of heat transfer is the goal of the ideal energy efficient homes, and double-glazed windows can help to achieve the goal. All high-performance windows have double glazing that works well in all kinds of climates, hot, cold, and mixed. For the best thermal performance, the norm is to use a low e-glass coating on one glass pane and fill the space in between the glazing with argon gas. The U-values of this type of double glass windows is as low as 1.8 which for normal single glazed windows can be as high as 5. The air gap can be as low as 6mm, but for all practical purposes, it is better not to maintain such a fine gap unless it is necessary because wider gaps of 10-20 mm improve U-value.
To complement low U-value glazing, you must choose a matching window frame whose U-value is also low so that cumulative effect translates into overall low U-value. For advanced thermal performance, it is advisable to use UPVC or wooden window frame or that made from composite material like aluminum and timber.
The window fitting plays an important role to improve insulation because loosely fitted sashes and frames provide an escape route for hot and cold air just as it can happen through cracks around the frames. Sealing windows to plug the gaps is essential to improve thermal insulation. Sliding windows with improved sealing are now available that matches with the superior air infiltration performance achieved by using compression seals fitted to casement and awning windows.
To compare window performance, you can refer to the WERS or Window Energy Rating Scheme that rates the energy impact of different types of windows based on the number of stars from 1 to 10. The more stars, the better.