Energy efficiency is critical but health must be protected.
Energy efficiency is critical on the path to net zero emissions because our current needs are considerable and replacing current building energy use with new renewable generating capacity (not using gas), energy storage and transmission capacity would be even more expensive. Efficiency is also beneficial in other ways including improving health and reduction of energy poverty. For example, in the past efficiency measures have contributed to sick building syndrome – to avoid this, air tightness must be accompanied by adequate ventilation. Also temperatures below 18°C can trigger health problems in vulnerable adults directly; there is evidence that 18°C is warm enough for most people [2].
Stringent energy efficiency standards make homes cheap to heat.
The PassivHaus energy standards are widely used for social housing as they reduce the energy bills for tenants. Lower bills and healthier tenants reduce costs for landlords too as tenants are less likely to fall into arrears with the rent [3].
Passivhaus standards for new build are achievable in all regions of the world.
There are many examples of Passivhaus certified buildings in the northern hemisphere where winters are cold but relatively few in the south where the main requirement is cooling[1]. The requirement for Passivhaus certification on a new build is that total heating and cooling energy demand should be no more than 15 kWh/m2/year (1350 kWh/year for a typical home with 90m2 floor area). For retrofit the requirement is less stringent, at 25 kWh/m2/year (2250 kWh/year). This is still huge reduction on typical UK homes where energy demand is typically 11,500 kWh/year for gas alone, ignoring electricity (according to British Gas).
Air conditioning will be more widespread by 2050.
Very few homes are cooleded with air conditioning, at the moment. However, climate change will make cooling more essential by 2050 [4]. Passivhaus standards are a challenge in hot humid regions. In regions where the main requirement is for cooling, even very efficient buildings can use 90-180 kWh/m2/year for cooling compared to 15 kWh/m2/year for heating. The heating requirement can be reduced by super insulation and ventilation with heat recovery (MVHR). Cooling that does not increase energy demand is best achieved by shading (such as deep eaves over windows) and stack effect natural ventilation. Sadly these are hard to retrofit. Also dehumidification may be needed as cooling humid air can lead to condensation which allows mould to grow.
Energy Efficiency in buildings has improved substantially since 2000 as shown by Figure 2 from [1].
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| Figure 2 from [1] showing decreasing energy use intensity for home energy since 2000. |
However, much of this improvement has been offset by increasing building size, especially outside Europe.
The best time to install energy efficiency is at build time or when maintenance is required.;
Retrofitting energy efficiency measures into existing buildings is often very expensive as well as a major hassle for residents. In comparison, the marginal cost for efficient components such as windows are often quite small in comparison to the anyway cost of replacement.
Energy efficiency retrofits can easily take 10-20 years for payback in lower bills and this is too long for most home owners or landlords. Hence financing packages are needed. Also these retrofits are a major hassle, requiring planning permission and contractors to be hired and managed. During the retrofit, parts of the building may be unusable or at least need to be emptied of furniture. Temporary accommodation may be needed. (We conducted our retrofit in phases, with each phase requiring some furniture moved into storage but we never moved out. This was possible because we live in a large home that is arguably under-utilised.)
One stop shops such as Action on Energy Cambridgeshire can reduce the hassle and facilitate access to funding schemes.
One stop shops can reduce the hassle, providing planning advice, project management and often access to finance. We used an architect for project management but there are also specialist firms such as Ecofurb. Some local councils offer a one-stop-shop service through a partner. Cambridgeshire uses Action on Energy
References
[1] Diana Ürge-Vorsatz, Radhika Khosla, Rob Bernhardt, Yi Chieh Chan, David Vérez, Shan Hu, and Luisa F. Cabeza, (2020) Advances toward a Net-Zero Global Building Sector, Annual Review of Environment and Resources
[2] (R. Wookey, Dr. A. Bone, C. Carmichael, A. Crossley, 2014) Minimum home temperature thresholds for health in winter – A systematic literature review (Public Health England) online.
[3] Sustainable Homes (2016) Touching The Voids: The impact of energy efficiency on social landlord income and business plans (2016), online
[4] J. Crawley, S. Ogunrin, S. Taneja, I. Vorushlyo and X. Wang, Domestic air conditioning in 2050 (UKERC, 2020)
