A variety of low, medium and high rise social housing types in north London, England.High rise apartments tower over local authority housing and flats amidst a splash of green trees. The tower blocks are lit by the evening sun against a backdrop of ominous black storm clouds

Tenant blowback hits heat recovery ventilation

Tuesday, February 2, 2016

Recent data analysis from the United Kingdom’s Building Performance Evaluation (BPE) program questions the suitability of some types of energy-saving technology for affordable housing projects. An assessment of social housing participating in the BPE program noted particular shortcomings with heat recovery ventilation, largely attributed to operations and maintenance limitations and/or building occupants’ interference, as well as a greater tendency for heat pumps and solar thermal systems to falter.

The BPE tests U-values, air tightness, indoor air quality and occupant satisfaction to plot how post-construction performance differs from the design intention. The analysis of social housing projects specifically focuses on those built by not-for-profit associations known as Registered Providers (RPs), which, for the study’s purposes, are deemed to have a more sophisticated approach to management and sustainability.

“RPs are different from many housing developers in that as owners of new properties they have long-term maintenance responsibilities — i.e. very clear means, and usually capability, to apply lessons from BPE projects into new developments,” the report states. “An additional benefit is that, across the sector, RPs have been very receptive to recognize that there is a significant gap between new-build specifications and real-life operation. Many RPs recognize that new in-house and supply chain skills are necessary to deliver energy-efficient and affordable social housing.”

More than two-thirds of analyzed dwelling units had heat recovery ventilation, eliciting almost the highest rate of building service issues among 25 evaluated technologies. (Air source heat pumps recorded a higher rate of issues, but served only 6 per cent of units.) On average, commissioning agents identified 1.14 issues per installation, including unbalanced systems, blocked filters and over-pressurization of the external fabric. Building occupants also undermined the systems through actions that, arguably, most people would consider reasonable, such as opening the window or turning the unit off to eliminate unwanted noise.

Analysts conclude the technology is not yet the right fit for the tenure. “Heat recovery integrated mechanical ventilation is projected to achieve the next steps in energy savings in high energy performance buildings where ventilation heat loss covers a predominant quota of the overall building energy demand. However, their current applicability in social housing is questionable as evidenced by the frequent occurrence of issues captured by the BPE evaluators,” the report states.

Findings related to space heating and renewable energy also underscore the need for operational skills and training. Far fewer building service issues were recorded with conventional boilers compared to exhaust air and air source heat pumps, biomass boilers and communal heating via combined heat and power (CHP). The wide range of different heat pump configurations is a suggested complicating factor given evidence that “the industry copes well with something established and relatively badly with newer technologies.”

Solar photovoltaic systems, which the report describes as a “well-established technology supported by quality assurance schemes” similarly engendered relatively few building service issues. In contrast, solar thermal garnered complaints about design, inaccurate specifications for controls and lack of coordination between contractors and installers, resulting in incorrect setup and unforeseen failures.

One thought on “Tenant blowback hits heat recovery ventilation

  1. Interesting article and reference document. It’s apparent that operable windows fall into the area of problematic technology. We need a reliable means of auto set-back on heating / cooling when windows are open to provide occupants with a thermal cue.

    I was appreciative of the process-related findings. For example, the report advocates:

    – integrated design process (participatory, multi-disciplinary) that extends past design and construction into the first 3 years of operation (“Soft Landings”)
    – use of sustainability certification systems, especially Passivhaus
    – envelope-first design strategy
    – wariness about non-conventional tech
    – inspection and testing of insulation and air-tightness during construction
    – cash holdbacks to encourage achievement of design intent
    – better documentation and training

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