Energy Use

ENERGYUSE
Comparison of energy use and comfort conditions in timber- frame and traditional block type houses


PROJECT LEADERMr Bill QuigleyNuTech ConsultantsPO Box 8008GlenagearyCo DublinTel: (01) 663 6372Email: bill_quigley@unison.ie


PROJECT TEAMMr Bill Quigley. Project Co-ordinator, NuTech Consultants.Mr Mark Forkin, Technical Advisor, NuTech Consultants.


OBJECTIVESAdvocates of timber-frame housing have long argued that timber-frame houses are more thermally efficient and therefore more cost effective to heat. However, it can be argued that building regulations specify a minimum thermal efficiency for building that must be achieved by all construction methods. This is true of calculated thermal efficiency (U- values), however, it has been shown that due to poor on-site practices, actual U-values achieved in practice can fall significantly short of the calculated values. This is why a factory based system such as timber frame has advantages over site based construction systems. The objectives of this project were to conduct a preliminary examination and assessment of timber-frame and hollow block built houses to ascertain the real differences in energy efficiencies.


PROGRESS TO DATEThree timber-frame houses and three traditional hollow block built houses were monitored over a three week period in March/April 2002. Energy audits were carried out for each house type. This consisted of a desk study to determine the heat losses through the various elements of the house. A comparison was made for each house type and method of construction. A calculated air infiltration rate was inputted into an energy model along with other elemental data. This model uses test reference year weather data from the Irish Meteorological Service to ascertain how much energy a specific house design, with a particular system of boiler and emitters, will use for space and water heating. The model also takes into account the Thermal Capacity of the building (measured in kiloWatt-hours per degree Celsius). The model predicted the annual energy usage for space and water heating for the houses in both groups.On-site monitoring was carried out in each of the houses to determine:Average house temperatures;Boiler run times;Decay temperatures when the heating is turned off, i.e. the rate of cooling down of each of the houses in each group;Outside air temperature.From these data, the heat loss characteristic for each house and the level of comfort experienced for the particular heating regime chosen by each set of occupants was determined. Data loggers with built-in thermisters and data loggers with PT100 external probes were used. The data loggers were set up to read temperatures at ten-minute intervals. Similar house styles were compared. Termon Abbey (left) was built using timber-frame construction and Elmfield Green (right) was constructed using the traditional hollow block method. Once the houses were finished it was difficult to visibly determine the type of construction used. However, the difference in thermal efficiency is notable.


RESULTSThis was a pilot study and as such the sample of houses involved was small. Nonetheless, the results indicate that using timber-frame construction will ensure that predicted savings will be achieved in practice. Further savings will be possible by taking advantage of the characteristics of timber-frame housing. From the energy viewpoint, this form of construction is ideally suited to the Irish climate. The major conclusion is that the timber- frame houses achieved a slightly higher average house temperature using less energy and hence at a lower cost than the hollow block built houses. Specifically, there was a 32% higher energy cost in the hollow block built houses than in the timber-frame houses. A second key conclusion is that the amount of energy required to maintain the desired comfort temperature above the external ambient temperature is considerably lower in the timber-frame houses. In fact, it takes 44% more energy to achieve a 1°C increase over the ambient temperature in hollow block built houses than in timber-frame houses.


OUTPUTSThe detailed final report will be published and circulated to all stakeholders.A follow-on study, at a much larger scale, may be undertaken, subject to the sourcing of available funding.


ACTIVITIES PLANNED FOR 2003The results will be of interest to all builders and prospective building owners/occupiers, especially as all commercial buildings sold or rented will need an energy efficiency certificate from 2005. A new EU Directive will insist that certificates are in place before any purchase or lease transaction is legally recognised. The Directive is being driven by the fact that 40% of greenhouse gas emissions in the EU come from buildings. Certificates will enable prospective tenants or owners to compare properties more easily. It is hoped that energy efficiency will become a major factor in purchasing and renting decisions. The results of this work indicate that the EU Directive would favour timber- frame construction. The results of this work will be circulated to local authorities, the National Building Agency, the Department of the Environment and Local Government and, through trade journals, to builders, developers, architects and engineers.


COMPLETION DATEThe research has been completed. The final report is being edited and will be placed in the public domain early in 2003.



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