Post-War Refurbishment: Making post-war era houses sustainable

The Netherlands faces climate change due to global warming and earthquakes due to gas production. To decrease both earthquakes and CO2 production, the government aims to half the gas production in the coming four years and aims for an entire stop by 2030. Over 80% of Dutch houses are heated with gas; 20% were built in the late post-war era (1960-1974) and these houses consume the most gas due to low levels of insulation. As most of these houses are very similar in construction they have a high potential for large scale refurbishment strategies. Therefore, the aim of this study was to create three strategies with each a different level of improvement, applicable to multiple building types of late post-war era houses. A row house was used to develop and test the strategies and a semi-detached and a free-standing house were used to test the versatility. Testing was performed with Design Builder and Uniec 2.2, both energy performance programs. Based on a literature review and analysis of the case study, the strategies developed were a basic insulation strategy (A), Energy Performance Coefficient (EPC) ≤ 0,4 strategy (B), and a Net Zero Energy Building (NZEB) strategy (C). Strategy A consists merely of basic insulation techniques and the upgrading of old heating systems, which lowers gas consumption with roughly 50% and has a payback time of roughly 15 years. The second strategy aims to lower the EPC to 0,4 or less as is required for newly built houses and consists of higher-level insulation techniques and the use of solar power for heating and electricity. This decreases gas consumption with roughly 75%, electricity consumption with over 45%, has a payback time of roughly 15 years, and a better balanced investment vs. yearly savings. Strategy C adds exterior insulation and installs a hybrid electric boiler, an air heat pump, and solar collectors resulting in a (nearly) NZEB and gas-free house. A very large investment is required for this strategy but the approximate 20 year payback time makes it worthwhile. The free-standing house was very similar in construction and the three strategies can easily be applied. Strategy A showed similar results, and remarkably both B and C showed both a higher reduction and shorter payback time than with the row house. With strategy C a NZEB could easily be achieved. The semi-detached house has an a-typical construction, monumental status, and air heating system and would require a specific strategy focussing on internal insulation and complete replacement of the heating and ventilation system. In conclusion, typical post-war era houses can easily be refurbished with these three strategies whereas a-typical houses will require a specific strategy. From a long-term societal perspective, I recommend the NZEB strategy. From the homeowner’s perspective, the EPC ≤ 0,4 strategy is probably the best achievable given the required investments. If we really want to reduce global warming and reduce gas consumption, major steps still have to be taken by the government and industry. Architecture, Urbanism and Building Science