Home Engineering Sustainable High Rise Buildings in Urban Zones: Advantages, Challenges, and Global Case Studies
Discussion and Conclusions
The discussion of the results is done in view of evaluating whether or not myths about building renovation are true. We use the observations and results of our investigation to provide the answer to “true or not?”
Myth: Regulations and laws are a good way of obtaining energy-efficient buildings with good indoor air quality.
This myth is not entirely true according to our investigation. The government can endorse laws with the purpose of improving energy efficiency and indoor air quality. Though the more recent building regulations state that buildings undergoing major renovation should strive to reach the same standard as set for new buildings, it is not compulsory. Therefore, the government does not in this case have the tools for improving energy efficiency in terms of building renovation. However, there are other laws that should be followed. Former building codes have always demanded that apartment be ventilated with at least a value corresponding to 0.5 ACH. The average value measured in this investigation is 0.41 ACH, where only three of 11 apartments would fulfill this requirement. The function check of the ventilation system is mandatory (OVK every three or six years, depending on ventilation system type) since 1992 and only five of 11 buildings has an approved certificate. EPC has been compulsory since 2008 and yet one of the 11 owners lacks the certificate for their property. EPC must suggest cost-efficient ECMs, but it is not mandatory to implement these. All in all, these numbers show that property owners either do not care for regulations and laws or are simply not informed or updated on these. The consequence is that targets are not achieved, even by legislation.
Myth: Heat recovery ventilation systems (HRX) always give substantial energy savings.
This is false according to our investigation. Retrofitting or improvements made in the building’s service systems (HVAC) are more economical than actions taken to improve performance of building constructions. HRX can give up to 30 % saving but also almost 0 %, generally not economical. One of the problems is that apartments often have inadequate ventilation rates. With a mechanical ventilation system, rates will in many cases be increased, thus reducing the saving potential but on the other hand enhancing indoor air quality. Another aspect that decreases efficiency is leaky envelopes. An alternative to HRX is to use exhaust air heat pump, which will have better efficiency than HRX but on at the same time increase the use of electricity. A HRX system has two fans that will increase the use of electricity and thereby also primary energy and emission (especially when calculating with marginal production).
Myth: New windows are always cost efficient and are payed off after 15 years.
Not true according to our investigations. Large savings can be obtained by improving the building envelope, for example with additional insulation and by replacing new windows with old. However, these measures are not profitable, independently of how and with what the building is heated. This indicates that energy prices are too low or that the measures are too expensive, except for extra insulation in the attic unless this has not already been done. The low prices on pellets and DH (both are renewables) make many measures expensive and become more-so in a region where the buildings are quite small, i.e., reducing transmission losses through the envelope become vital to reduce energy use, but expensive. New windows are not profitable. A cheaper option is to fit an extra pane in the old window (if the condition allows this measure) but is only profitable in electric heated buildings (which have the highest heating cost). Worth noting—only building No. 8 (oil) shows profitability of extensive additional insulation on external walls (it is actually more profitable to change the heating source to a GSHP or a pellets boiler as shown in Akander et al. (2012).
Myth: Solar energy is not profitable in Nordic climates.
Not true according to our investigations. Solar energy is, despite the latitude of the region, economically viable—especially PV solar energy. This quite unforeseen result rendered interest among building owners. However, in a broader perspective, the question is if it is worthwhile to invest thermal solar energy in DH areas that to a large extent uses waste heat and relatively cheap renewable fuels (in this case to a large extent forestry production waste). In essence, solar thermal energy is replacing other cheap or renewable energy in the non-heating season. Photovoltaic panels (PVs) are viable—the combination of PVs and DH is beneficial since saving electricity is more important than thermal energy in DH areas, see Truong et al. (2014) and Thygesen and Karlsson (2013). However, the market situation is influenced by politics and for the time being, property owners can sell produced solar electricity to tenants. Excess production can be sold via the grid, but is not economical. The calculations are based on month-wise debit and no subsidies for installation of the PVs. Today, PV debit is on daily basis which require tax cuts for small-scale producers in order to make the technology and installation viable.
The predicted impact of each package is shown for two scenarios of electricity production—based on the national average value and on Nordic marginal production value
Myth: Heat pumps (HP) use less energy than DH, which motivates use of HP in DH-heated areas.
Not entirely true. From owner perspective, the running cost of a HP seems less than for DH (if investment costs are disregarded) primarily due to the HP coefficient of performance COP. When looking at P.E. and emission, the situation becomes different since the national mix value of electricity production gives approximately the same as for DH while results for the marginal value show that a HP will use more natural resources than DH and increase emissions. Since marginal values are recommended to be used in predictions or planning phases, the results suggest that the use of HPs in DH areas is not a good choice in terms of resources and environment.
Myth: Deep renovation of multifamily buildings is not worthwhile—it is better to tear down old buildings and erect new ones.
This may be partially true and depends on the overall condition of the building. In terms of energy use, a 50 % reduction is technically and practically possible but not profitable. Deep renovation in real projects costs some 680-2300 €/m2 (Byman and Jernelius 2012) of which about 20 % of the total cost is dedicated to energy measures (thus 120-680 €/m2) where reductions of up to 70 % have been obtained. In the four projects presented in Byman and Jernelius (2012), the rent was increased with 7, 20, 35, and 40 %, respectively. In two projects, the renovations were considered to be profitable while the other two were more “goodwill”. This should in turn be compared with the cost of a new multifamily building, which on a national basis (excluding Sweden’s three largest cities) averages to about 3000 €/m2 (SCB 2012) (this excludes the costs of disassembling the old building).
In this investigation, calculations indicate that energy reduction would cost approx. 120-540 €/m2 to reach 50 % cuts, corresponding well with the real projects. Average costs of Packages 1, 2, and 3 are 228, 246, and 62 €/m2 with the latter giving a 17 % saving in energy use.
A reduction of energy use by 50 % is possible in deep renovation. However, energy savings will not cover the renovation costs. Other factors such as socioeconomical and increased rents must be considered in order for the measures to be profitable.
Myth: Newly erected buildings are more energy efficient than old buildings.
This is only partially true. Statistics in Fig. 8.2 illustrates that buildings that were erected in the 1990s have poorer energy performance than those that were built after the oil crisis, primarily during the 80s, when building codes became stricter. The group that shows the worst performance is that of the 1970s, i.e., older buildings are apparently more energy efficient. This group stands next in line to be renovated, since major renovation is performed every 40th year. It is therefore important to use this occasion to perform substantial ECMs in this renovation process, since it will take another four decades until the next time which is beyond 2050 and by then used considerable amounts of primary energy and released vast quantities of CO2. This investigation shows that there are potentials of creating sustainable energy-efficient renovated old buildings.Acknowledgements Funders of the EKG project are acknowledged: Swedish Energy Agency, Regional Council of Gavleborg and University of Gavle. The authors are in debt to co-workers Gustav (Persson) Soderlind, Linn Liu and Sanne Godow-Bratt.
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