Adapting 1965-1980 semi-detached dwellings in the UK to reduce summer overheating and the effect of the 2010 Building Regulations

Author: Steven Howse

Abstract

The aim of the report was to produce recommendations for occupants to undertake, concerning passive changes to the building design and changing occupant activity to reduce overheating in 1965- 1980 semi-detached dwellings. To do so, interventions in these two topics were tested to reduce overheating on a post 2010 Building Regulations base case.

This base case and interventions simulations were developed using IES software. To measure the level of overheating, internally, a degree hours over the CIBSE overheating threshold (CIBSE, 2006) method was used.

The basic upgrades to the building implementing the 2010 Building Regulation were found to decrease the total degree hours. When changed to two elderly (vulnerable) occupants, the total degree hours decreased overall. Other interventions that were found to decrease the total degree hours below the 2010 Building Regulation model were the updated appliances/occupancy trends, the cross ventilation strategy, north orientation and most prominently, the nigh time ventilation. A combined model of these interventions were then able to remove all degree hours beyond the threshold, even in a heat wave simulation; for both occupancy types.

As well as the combined intervention model, external wall paint shutters and curtains (sourced from previous research) are recommended for reducing overheating, based on ease-of-use and cost.

Executive summary

In the UK, there is a growing debate over the importance of decreasing winter fuel allowance through energy efficient upgrades to the building fabric against their effect on summer overheating. The focus of this report is to present a set of design and occupant recommendations on what occupants can do to passively reduce overheating in their 1965-1980 semi-detached dwellings. This is achieved by testing changes to occupant behaviour and building aspects; through different interventions, post 2010 Building Regulations.

IES software was chosen to simulate the different scenarios of possible interventions to overheating upon a base case design of a four person family 1965-1980 semi-detached dwelling. Standard dimensions, materials, occupant/appliance gains and time profiles were chosen to justify the base case. To measure the degree of overheating internally in the dwelling, a degree hours over the CIBSE overheating threshold (CIBSE, 2006) was used. This method measures the severity of overheating and allowed the comparison of the effect of these interventions on key rooms.

Figure 1 - Comparison of degree hours above the threshold (26°C/28°C) temperature for 1965-1980 semi-detached dwelling and rooms, testing different interventions

The basic upgrades to the building with the improved U-values of the 2010 Building Regulation were found to decrease the total degree hours; dispelling the main theory of health risk associated with improving the air tightness of the dwelling. When changed to two elderly (vulnerable) occupants, the total degree hours decreased overall compared to the original family profile. From the multiple interventions there are many that were found to increase the total degree hour of the dwelling.

Methods such as daytime single sided ventilation and east/west orientation were the most costly interventions, although there were question on the legitimacy of the increase in degree hours caused by external insulation. On the other hand, interventions that were found to decrease the total degree hours below the 2010 Building Regulation model were the updated appliances/occupancy trends, the cross ventilation strategy, north orientation and most prominently, the nigh time ventilation.

From the comparison of all the simulations combined (Figure 1), none of the proposed simulations were individually able to remove total degree hours over the threshold. However when combining the effective interventions, the generated results showed even in heat waves it was able to remove risk of overheating altogether (Figure 2). Although in the family heat wave scenario, the 1% over the threshold maximum was noted. (CIBSE, 2006)

Overall in merging both the combined reduction techniques of this particular study with a previous study, a definitive set of recommendations were made. Taking into account both the ease of implementation and cost of the method, as well as the previously stated degree hours reducing interventions, external wall paint, shutters and curtains could be used.

Figure 2 - Comparison of degree hours above the threshold (26°C/28°C) temperature for 1965-1980 semi-detached dwelling and rooms, testing different interventions

In the wider relevance of the research, it can be used to judge the severity of risk that it may cause to occupant health. Furthermore, it can be used to adapt more criteria in current guidance reports for overheating, with the interventions tested on other types of dwellings.

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This paper was entered into a competition launched by --BRE Group and UBM called to investigate the link between buildings and the wellbeing of those who occupy them.