Matthew Vong, M.Eng. 2013
Supervisor: Dr. Rodrigo Mora
Windows have become popular in current high-rise construction; many new constructions have upwards of 80% window to wall ratios (WWR). Research has shown that the higher glazing ratios have contributed to an increase in the energy consumption of buildings, in particular multi-unit residential buildings (MURBs). It is known that windows have both benefits and limitations in its effect on building performance. In particular, windows are the worst performing component in terms of thermal resistance within the building envelope, which contributes to higher energy use in buildings.
The need for energy-efficient buildings is recognized in the industry, with building codes becoming more stringent. New constructions will have to demonstrate improved energy performance, measured through systems such as LEED, in order to receive building permits. Since many new designs are highly glazed, the impact of windows on building performance is magnified, and window selection is critical in meeting energy efficiency and sustainability objectives. It has been shown that improved windows, such as triple glazing and argon filled windows, can improve building energy performance, measured through energy use intensity (EUI).
Building energy simulation is a widely used tool to compare how different building design options, such as fenestration, impact building EUI. Even though building energy simulation can be a very powerful and useful tool in design, it is imperative that the inputs and assumptions are sound in order to generate accurate and meaningful results. In recent years, simplified energy simulation tools, which analyze only fenestration, have been developed. These tools require minimal inputs, and can be an asset in early stage design where information may be limited and where the length of time associated with developing a whole building simulation model may not be feasible.
Through interviews with building energy modeling professionals, and review of various published guides on energy modeling, a flowchart with an accompanying table have been developed, which synthesizes the energy modeling process for engineers and architects to follow so that building energy simulation can be used to aid in selecting the optimal glazing for a particular building. Additionally, the use of COMFEN, a fenestration only energy simulation software for early stage design, was validated by comparing results generated to that of eQuest, a whole building energy simulation tool widely used in the industry. Results from COMFEN showed a similar trend to those of eQuest, proving COMFEN to be a suitable tool for early stage design use.
To demonstrate the methodology proposed in the flowchart and table, a case study is presented, from building the model in energy simulation software to results analysis. Glazing properties which affect building EUI were simulated one by one and graphed individually to show their respective impacts on EUI at various WWRs. Overall, the methodology proposed was successful in identifying glazing options which would lead to the best energy performance in the case study building.