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Energirenovering af typisk parcelhus opført i perioden 1960-1980. Del 1 Beregninger

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Report R-165: Energy renovation of a typical Danish single-family house from the 1960-80’s. The report documents that the energy consumption for heating, cooling and ventilation in a typical Danish single-family house from the 1960-80’s can be reduced by 60%. The house is a typical one storey house built in 1972 with a heated gross floor area of 155 m2. It was achieved using relatively simple improvements of building envelope constructions and heat and ventilation systems. The documentation has been carried out using the programme Be06, which is the official Danish calculation tool to be used in the assessment of the energy performance of buildings. The calculation method used in the programme is of course based on relevant European standards (e.g. heating requirements based on pr EN ISO 13790), and the calculations are carried out on a monthly basis. The programme input was based on “Handbook for Energy Consultants 2008” which is used by Danish energy assessors carrying out assessments and producing Energy Performance of Buildings Certificates. The calculated energy performance before the renovation was 272 kWh/m2 per year. After the renovation it has been reduced by 60% to 109 kWh/m2 per year. The energy frame of a new house is 89 kWh/m2 per year. Consequently the house was brought up to almost the energy performance level of a new house. As a positive side effect, the living conditions have been greatly improved due to the insulation, air tightness measures, and the introduction of mechanical ventilation with heat recovery. The house has achieved an Energy Certification of F before the renovation and a C after the renovation (based on a scale from A-G). This corresponds to a significant improvement. The existing building envelope construction consisted partly of 300 mm insulated cavity walls with 75 mm of insulation, steel ties, and an outer leaf of 110 mm masonry and an inner leaf of 100 mm light-weight concrete or 110 mm masonry. Parts of the external walls were originally framed walls with studs of timber and with an insulation thickness of 75 mm, which was later increased by 125 mm. The fairly large areas of windows were traditional old wooden windows with double-pane glazing. The roof with one half of it having a ceiling to the ridge and the other half with a normal flat ceiling were insulated with 100 mm and 300 mm of mineral wool, respectively. The slab on ground construction had an insulation thickness of only 30-50 mm. The energy saving measures carried out were: • Insulation of the building envelope: External insulation of walls (100-150 mm), External insulation of foundations, 45 cm below ground (100-225 mm), External insulation of the ceiling to the ridge (345 mm) (no extra insulation of the flat part) • New windows: New slim framed wooden windows and external doors with double-pane low-e-glazing, New triple-pane low-e-glazing with krypton in the large glazing facades • Changed ventilation: Air tightness measures regarding building envelope, Installation of a mechanical ventilation system with high-efficiency heat recovery (Nilan Comfort 300T EC) • New gas boiler: New high-efficiency condensing gas boiler (Viessmann Vitodens 300), insulated hot-water tank and new thermostatic valves. • Low temperature operation of the heating system: Related to the improved insulation of the envelope which means that the water based heaters can yield sufficient heat even though the temperature is lower, which results in a reduced heat loss from the heating pipes placed in the concrete slab of the slab on ground construction. The reduction in the energy requirement for the different energy saving measures is interesting and is evident in the table below. The method used is the same as Danish energy consultants’ use, i.e. each individual energy saving measure is calculated separately. It should be noted that the sum of the energy savings is somewhat larger than when calculated with all measures included. The calculations show that insulation of the building envelope saves 26% of the total energy savings, while new windows also save 26 %. The share of reduction regarding the changed ventilation is 23%. The replacement of the boiler contributes 20% to the savings and the low temperature operation of the heating system 5%. Based on these calculations, it can be concluded that about 50% of the energy savings is related to the building envelope and that the other 50% is due to heating and ventilation related measures. The calculation of the effect of the comfort improvements, i.e. roof windows and circulation of domestic hot water, shows that the energy requirement after the renovation will increase 11%. The calculations were carried out using standard assumptions from the energy certification scheme regarding indoor temperature, required domestic hot water and user behaviour. This implies the possibility of significant differences in the calculated effects of the energy saving measures, and the actual gained savings as user preferences – like the actual indoor temperature conditions, electricity consumption, opening of windows, weather conditions etc. – play an important role for the real energy requirement.

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