Passive House Design (PHD)[i] is a set of principles meant to make a building energy efficient by cutting back on consumption rather than implementing new technology. Figure 5[ii] below shows the residential energy usage in single-family US homes. Space heating and cooling account for a large sector of energy usage. PHD works to address heating and cooling concerns without requiring advanced building technology. Criteria for PHD vary based on climate, but they all employ the following:
- Continuous insulation through building envelope
- Minimal space conditioning
- Airtight building envelope
- High-performance windows
- Balanced heat- and moisture-recovery ventilation
- Solar gain used to exploit sun’s energy for heating, while minimizing overheating during summer months
Creating a PHD building costs about 5-10% more than a conventional build. Cost of the aforementioned criteria decreases as you scale, so multifamily residential buildings often find it is feasible to incorporate PHD without significant cost burden. When seeking sustainable design, PHD is a well sought after solution, as it doesn’t come with the high implementation costs that you see with renewable technologies such as solar arrays and geothermal heating systems.
Net-zero buildings[iii] are defined as buildings that produce as much energy through renewable sources as they consume over the course of a year. A net-zero community has the same requirement applied to a network of buildings, both residential and commercial. To achieve net-zero status, buildings must incorporate renewable energy systems and energy efficient appliances and design criteria.
Energy storage is an optional but integral add-on in net-zero systems. Storage is used minimally as it stands, but technologies are developing rapidly and will hopefully rise in capacity and lower in cost in the near future. Because renewable generation is not consistent and reliable, storing energy during overproduction times to be used when energy is not being produced would eliminate dependence on the utility grid. As it stands, most homes that have solar arrays or use alternate renewable energy sources must still connect to the utility grid to use as backup if their system cannot meet demands. In places with poor net-metering policies, grid-independence would be beneficial from a financial standpoint as well, for homes could generate all of their own energy and anything unused would be stored for future consumption.
[i] Passive House Principles. Passive House Institute US, 2018.
[ii] Kapsalaki, M. et al. A methodology for economic efficient design of Net Zero Energy Buildings. Energy and Buildings 55 (2012), 765-778.
[iii] Rosen, M.A. Net-Zero Energy Buildings and Communities: Potential and the Role of Energy Storage. Journal of Power and Energy Engineering, 3 (2015), 470-474.