low carbon home

Low carbon buildings and homes are new and there are still many areas of uncertainty around their operation. New research results show how the satisfaction and behaviour of occupants can be improved resulting in buildings achieving the energy savings they were supposed to, which isn't always the case.

The new research covers firstly the tests used to determine whether the buildings actually deliver the savings predicted, secondly how to communicate with occupants so that the expected savings are delivered, and lastly how mechanical ventilation and heat recovery (MVHR) units perform in practice.

Co-heating tests

So-called co-heating tests are used to measure overall heat loss from buildings, and have been found to produce results quite different from those predicted. It was thought that it was because people inside the buildings behaved in a way that was inappropriate to buildings constructed with passive house principles, for instance by opening windows when unnecessary.

But new research by the NHBC Foundation shows that in fact many of the inconsistencies are due to the weather. It means that the tests are not as accurate as they were supposed to be for reliably evaluating energy performance.

The co-heating test, designed in its present form by Leeds Metropolitan University, provides a means to measure as-built performance. It works by heating the interior of a building to a uniform temperature and then recording the amount of electrical energy needed to retain this temperature over a period of around two to three weeks.
Experts from seven different organisations carried out a number of co-heating tests on the same houses. The results produced varied widely, with the lowest 17% less than the SAP-predicted value (indicating an energy demand significantly less than expected) and the highest 11% more than the SAP value (indicating a much higher energy demand than expected).
The study found, perhaps unsurprisingly, that solar gain is the single largest cause of the difference. It advises that developing revised protocols for co-heating tests could lead to a more reliable test that would be more useful for house-builders’ R&D.

Educating the occupiers

Low- and zero-carbon (LZC) energy technologies are increasingly being adopted in the design of new homes. But many owners and occupiers will not be accustomed to the use of these carbon-saving heat and power technologies, and there is evidence that they are often misunderstood and incorrectly used.

This presents a potential risk that this could lead to dissatisfaction with new low-carbon homes, because of higher than expected energy bills, and to carbon emissions targets not being met in practice.

This means that it's important to understand whether occupiers can easily understand how to use the technology, whether their behavior needs to change to secure the benefits from the technology and whether we can plausibly expect that change to occur.

The research explored how occupiers’ behaviour can be affected by LZC technologies, and how they might be encouraged to willingly adapt to them.

It involved two sets of interview case studies:

  1. consumers and their reactions to LZC technologies 
  2. house builder sales teams selling enhanced homes with LZC technologies.

Observations from these were aligned with a continuous improvement cycle, which embraced key marketing considerations: Design & Production, Imagination, Purchase, Identification, Function and Feedback & Opinion.

With occupiers, the main findings were that:

  • households did not understand the underlying principles of the LZC technologies, but more than half felt comfortable operating them;
  • more than half would recommend their technologies to friends, but consumers were largely unable to articulate the benefits clearly;
  • none felt the written guidance on use of the technology was suitable and generally consumers felt that there was insufficient effort made to spark their imagination on the benefits and opportunities of having LZC technologies in their homes.

With sales staff the research identified:

  • that site staff and sales staff had taken time to communicate over the technologies installed; 
  • a varied level of understanding among sales staff of the specific LZC technologies being offered, and no clear feedback route from the consumer to inform the sales approach or the basic design of the home;
  • a very limited ability or willingness to communicate the benefits and opportunities in a way that the consumer could understand or be inspired by.

One of the principal suggestions arising from the findings is that house builders should consider how their sales teams appeal to the imagination of purchasers and inspire them to interact effectively with the technologies.

House builders should also actively seek feedback on operation, particularly when consumers’ lifestyles are compromised in any way by LZC technologies. The problem is that this is unlikely to happen since, once having built the houses, the developers move on to the latest project and lack the financial incentive to remain involved.

Do MVHR systems installing new buildings work?

This primary research report presents the findings from a two-year research project carried out by BRE entailing assessment and monitoring of 10 zero carbon Code for Sustainable Homes Code (CSH) Level 6 homes at Scottish and Southern Energy’s (SSE’s) Greenwatt Way development at Chalvey, near Slough, Berkshire.

Thanks to the cooperation and level of engagement from SSE it was possible to study the homes to some extent during construction and then to monitor them for a period of almost two years post-occupancy.

As well as inspection, testing and monitoring work it was possible to obtain occupant feedback and gauge perceptions of living in the zero carbon homes by use of questionnaires, walkthrough interviews and focus groups.

In addition to continuous monitoring of temperature, humidity and power consumption by the mechanical ventilation and heat recovery (MVHR) systems, periodic testing of indoor air quality and airtightness was carried out. Towards the end of the project a study was undertaken in one of the homes in which air quality was monitored during gas and electric cooking, with the ventilation system on and off.

Occupant feedback regarding living in the homes and general comfort was mainly positive, with levels of satisfaction tending to increase over time as the homes and their MVHR systems became more familiar.

Much of the negative feedback associated with ventilation, thermal comfort and internal noise could be attributed to the MVHR systems, including issues with perceived lack of control, temperature differences between storeys, experiences of draughts from cool air dumping and levels of mechanical noise.

Levels of satisfaction on these particular issues generally improved when remedial works were carried out on MVHR systems after one year of occupancy in nine out of the 10 cases.

However, the occupants in this particular study were judged to have been better informed than the average householder, and have benefited from the interventions carried out as part of this research project. In the wider world there would seem to be every possibility that, where MVHR systems are not designed, installed and operated correctly, house occupants may take radical steps in response to problems with their indoor environment – such as turning the MVHR system off.

In all cases, therefore it seems that designers, developers, installers and builders of new products for low or zero carbon buildings need to take a much more proactive position on after sales care and service to avoid a potentially damaging backlash amongst consumers.