Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Low-temperature Heating in Existing Swedish Residential Buildings: Toward Sustainable Retrofitting
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.ORCID iD: 0000-0001-6266-8485
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

As an energy-efficient alternative in cold climate countries such as Sweden, low-temperature heating (LTH) technology has shown promising advantages and shortcuts to contribute to the efficiency of heat supply, as well as to the overall sustainability of building performance. The goal of this thesis is to contribute to the development of methodologies and modeling tools to support sustainable retrofitting in the Swedish housing stock. A combination of three integrated modeling techniques was developed. The main focus of this work was implementing LTH in retrofitting practice. The principle of the developed methods can be regarded as a top-down approach, underpinning the general definition of LTH and sustainability criteria. It was found that a preliminary compilation and investigation of the building typology could simplify the retrofitting decision-making. Also, 36–54% of final energy savings could be achieved in studied housing archetypes by effective energy retrofitting. Combining LTH radiators with ventilation heat recovery showed the largest contributions. Below 30 W/m2 (12 W/ m3) heating demand, both radiators (ventilation radiators and baseboard radiator) could work as LTH. These reduced supply temperatures further improved the COP of air-source heat pumps by approximately 12% - 18%. For retrofitting of conventional radiators, there was no concrete evidence to support Type 22 having higher thermal efficiency than Type 21, for the Swedish climate and heating seasons. The achievements and full potential of implementing LTH in retrofitting were found to require not only efficient radiators, but also a well-designed package – insulation, piping, pumping and energy supply system - that suited the current heating demand of the building, given the local climate condition.

However, it should also be highlighted that retrofitting incorporating all evaluated measures would not always yield higher long-term economic profits among different archetypes. It is important to find the trade-off between cost-effectiveness and energy savings in similar archetypes - instead of using a “one size fits all” types of solution. For conventional retrofit measures, such as insulations of building envelopes, it was necessary to evaluate the embodied energy during the whole retrofitting process.

Abstract [sv]

Den ökande relativa energianvändningen i bostadsbyggnader i stadsmiljö har lett till högre krav på energieffektivit och hållbar omvandling av redan existerande bostadsbyggnader. En viktig förutsättning för att genomföra en sådan omvandling är att först utveckla metoder för hur effektiva beslut om renovering ska ske, samt att utveckla teknik för hållbar renovering. Lågtemperatursuppvärmning (LTH) har visat sig ha fördelar som ett hållbart och energieffektivt alternativ i länder med kallt klimat som Sverige. Metoden bidra till ökad effektivitet för uppvärmning och minskade energibehov för byggnadskomplexet. Det saknas fortfarande flera steg för hur man ska utforma modelleringsverktyg och utveckla kostnadseffektiva metoder för beslutsfattning och implementering av LTH i redan existerande byggnader. Dessutom försvårar avsaknaden av dessa verktyg och metoder genomförandet av kritiska utvärderingar av renoveringsalternativ utifrån hållbarhets- och effektivitetssynpunkt med huvudfokus på energibesparingspotential, miljöpåverkan och nöjdhet hos de boende. Dessa frågor undersöks i denna avhandling i samband med renovering av existerande bostadsbyggnader i Sverige.

 

Målet är att bidra till utvecklingen av metoder och modelleringsverktyg för hållbar renovering. Under arbetet utvecklades tre modelleringskoncept som integrerats med varandra och som svarar för olika steg i renoveringsmodelleringen. Huvudfokus i arbetet var att göra LTH till en del av vår renoveringspraxis. De renoveringsalternativ som studerats i arbetet inkluderar renovering av klimatskalet för att minska energibehovet samt implementering av LTH-radiatorer och där påvisa deras fördelar för valt primärenergisystem. Analysen omfattar även den sammantagna effekten av och de ömsesidiga beroenden som föreligger mellan olika renoveringsåtgärder. Här utvecklade metoder kan sägas följa en ”uppifrån och ner” strategi och stärker LTH som ett uppvärmningsalternativ som uppfyller hållbarhetskriterier.

 

Avhandlingen visar att effektiv renovering av energisystem kan minska det slutliga energibehovet med 36-54 % i de studerade byggnadstyperna. Kombinationen av LTH-radiatorer med värmeåtervinning från ventilation gav de allra största positiva bidragen. LTH-radiatorerna (ventilationsradiatorer och värmelister) fungerade som lågtemperatursuppvärmning vid uppvärmningsbehov under 30 W/m2 (12 W/ m3) och som ultra-lågtemperaturuppvärmning vid uppvärmningsbehov under 10 W/m2 (4 W/ m3).

De låga framledningstemperaturer som leds till LTH-radiatorer bidrar dessutom till att öka COP (värmefaktorn) för luftvärmepumpar med 12 – 18 %, jämfört med traditionella radiatorer med lika stor värmeavgivande area.

Något konkret stöd fanns inte för att Typ 22-radiatorer (dubbel konvektionsplåt) skulle ha högre värmeeffektivitet än Typ 21-radiatorer (enkel konvektionsplåt) för svenska klimatetförhållanden. Ökat antal konvektorplåtar visade sig alltså inte nödvändigtvis leda till ökad värmeeffektivitet.

Tröskelvärdet för när Typ 11-radiatorer (enkel panel) presterar sämre än den mest effektiva radiatortypen, Typ 21-radiatorer (dubbel panel) som även har bättre exergiprestanda, visade sig vara ett värmebehov av 480 W/rum.

För att uppnå full potential för LTH-radiatorer som renoveringsalternativ visade det sig utöver mer effektiva radiatorer även behövas ett välutformat system av rör, pumpar och energitillförsel, anpassade till byggnadens värmebehov före renovering vid rådande klimat.

 

Renovering som inkluderar alla möjliga alternativ leder inte alltid till högre långsiktig ekonomisk avkastning. Det är viktigt att finna en balans mellan kostnadseffektivitet och energibesparing för likande byggnadstyper, i stället för att utveckla en enda lösning som ska passa överallt. För traditionella renoveringsalternativ, så som isolering, var det nödvändigt att utvärdera den inbäddade energin under hela renoveringsprocessen. Stor risk för överskattad hållbarhet föreligger om man inte beaktar detta.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , 69 p.
Series
TRITA-STKL, 2016:01
Keyword [en]
Retrofitting, Low-temperature heating, Energy efficiency, Sustainability, Swedish residential buildings
Keyword [sv]
Renovering, Lågtemperatursuppvärmning, Energieffektivitet, Hållbarhet, Svenska bostadsbyggnader
National Category
Building Technologies
Research subject
Energy Technology
Identifiers
URN: urn:nbn:se:kth:diva-192958ISBN: 978-91-7729-126-8 (print)OAI: oai:DiVA.org:kth-192958DiVA: diva2:974035
Public defence
2016-10-20, F3, F3, Lindstedtsvägen 26, KTH Campus, Stockholm, 13:30 (English)
Opponent
Supervisors
Projects
D6559
Note

QC 20160929

Available from: 2016-09-29 Created: 2016-09-23 Last updated: 2016-09-29Bibliographically approved
List of papers
1. A methodology to assess energy-demand savings and cost effectiveness of retrofitting in existing Swedish residential buildings
Open this publication in new window or tab >>A methodology to assess energy-demand savings and cost effectiveness of retrofitting in existing Swedish residential buildings
2015 (English)In: Sustainable cities and society, ISSN 2210-6707, Vol. 14, no 1, 254-266 p.Article in journal (Refereed) Published
Abstract [en]

Swedish residential buildings are typically retrofitted on a case-by-case basis. Large numbers of building consultants are involved in the decision-making, and stakeholders find it difficult to quantify the sustainable profits from retrofits and to make an efficient selection of the optimal alternative. The present paper presents an approach to design and assess energy-demand retrofitting scenarios. This aims to contribute to retrofitting decision-making regarding the main archetypes of existing Swedish residential buildings and to the evaluation of their long-term cost effectiveness. The approach combines energy-demand modeling and retrofit option rankings with life-cycle cost analysis (LCCA). Four types of typicalSwedish residential buildings are used to demonstrate the model. Retrofits in the archetypes are defined,analyzed and ranked to indicate the long-term energy savings and economic profits. The model indicates that the energy saving potential of retrofitting is 36-54% in the archetypes. However, retrofits with the largest energy-saving potential are not always the most cost effective. The long-term profits of retrofitting are largely dominated by the building types. The finding can contribute to the standardization of future retrofitting designs on municipality scale in Sweden.

Keyword
Energy demand savings, Retrofitting, Swedish residential buildings
National Category
Energy Systems
Identifiers
urn:nbn:se:kth:diva-167770 (URN)10.1016/j.scs.2014.10.002 (DOI)2-s2.0-84926286891 (Scopus ID)
Note

QC 20150526

Available from: 2015-05-26 Created: 2015-05-22 Last updated: 2017-12-04Bibliographically approved
2. A novel hybrid methodology to evaluate sustainable retrofitting inexisting Swedish residential buildings
Open this publication in new window or tab >>A novel hybrid methodology to evaluate sustainable retrofitting inexisting Swedish residential buildings
2015 (English)In: Sustainable cities and society, ISSN 2210-6707, Vol. 16, no C, 24-38 p.Article in journal (Refereed) Published
Abstract [en]

Energy and environmental issues are increasingly important in existing building service and energy systems around the world. Despite great efforts to implement retrofit techniques in Sweden, no stringent evaluation of the benefits of these techniques or their systematic design has been completed. Traditional evaluations have not taken into account the embodied energy and greenhouse gases emissions of different retrofit options. This omission leads to underestimation of the potential environmental benefits of modern retrofit techniques. In this study a novel hybrid modeling approach to quantify the sustainability of retrofit options is developed to fill these knowledge gaps. The compatibility of environmental and energy saving modeling of various energy-saving techniques for future transition of Swedish residential building stock is analyzed. Consolis Retro and the life cycle assessment (LCA) techniques are employed and further coupled to simulate retrofit options. The model integrates both energy demand (net operational energy), primary energy (operational energy from energy mix to buildings) into evaluation criteria. Embodied energy (energy required to produce materials of retrofitting options) and embodied greenhouse gas emissions (upstream CO<inf>2</inf> equivalent) are introduced as new measures in the evaluation criteria. The results showed that low-temperature heating retrofitting was the most effective option from both a primary and embodied energy perspective in the studied building types. Combining circulation pump renovations could further contribute to the efficiency of low-temperature heating for energy-demand savings. High operational energy-saving measures may not always lead to larger reduction in both embodied energy and greenhouse gas emissions, particularly for building envelope retrofitting. Neglecting the embodied energy of retrofit options will increase the risk of overrepresenting their energy-saving contributions. The sustainability improvements of retrofitting, particularly large-scale measures, should take into account the embodied energy and greenhouse gas emissions from the material productions.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
Embodied energy, Retrofitting, Sustainability
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-166906 (URN)10.1016/j.scs.2015.02.002 (DOI)000367396200003 ()2-s2.0-84927936355 (Scopus ID)
Note

QC 20150608

Available from: 2015-06-08 Created: 2015-05-21 Last updated: 2017-12-04Bibliographically approved
3. Retrofitting with low-temperature heating to achieve energy-demand savings and thermal comfort
Open this publication in new window or tab >>Retrofitting with low-temperature heating to achieve energy-demand savings and thermal comfort
2015 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 109, 217-229 p.Article in journal (Refereed) Published
Abstract [en]

Low-temperature heating (LTH) has shown promising advantages and shortcuts to improve the thermal performance of radiators. An investigation on which renovation measures from the demand side, can cope with LTH or should be selected as ‘pre-retrofit’ to provide building performance improvements, were carried out in this study. IDA ICE was selected to perform the simulation of a typical Swedish multi-family archetype. Five common energy-demand retrofit options were analyzed. Thermal performance and operational energy savings before and retrofitting were in focus. The results showed that LTH with each of the energy-demand retrofit options can improve the thermal performance to an acceptable level. LTH-combined ventilation retrofitting showed the highest contribution in air temperature, predicted percentage of dissatisfied, and energy savings for space heating. Combining LTH with external wall retrofitting showed the highest effect in operative temperature and total operational energy savings. Combining LTH with all energy-demand retrofitting as a package can achieve 55.3% and 52.8% total delivered and primary energy savings, respectively. This research showed that the existing building can cope with LTH when any of the five energy-demand retrofit options from a thermal performance perspective. Optimal selection shall be based on their abilities to reduce operational energy.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
Retrofitting, Low-Temperature Heating, Operational Energy, Thermal Performance, Swedish Low-Rise Residential Buildings
National Category
Building Technologies
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-175386 (URN)10.1016/j.enbuild.2015.09.047 (DOI)000367115300020 ()2-s2.0-84970016454 (Scopus ID)
Note

QC 20151110. QC 20160121

Available from: 2015-10-13 Created: 2015-10-13 Last updated: 2017-12-01Bibliographically approved
4. Ventilation heat recovery jointed low-temperature heating in retrofitting: An investigation of energy conservation, environmental impacts and indoor air quality in Swedish multifamily houses
Open this publication in new window or tab >>Ventilation heat recovery jointed low-temperature heating in retrofitting: An investigation of energy conservation, environmental impacts and indoor air quality in Swedish multifamily houses
2016 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 121, 250-264 p.Article in journal (Refereed) Published
Abstract [en]

Sweden is actively engaged in accelerating the sustainable transformation of existing building and energy systems. Most traditional investigations of this subject have been based on final energy savings and CO2 emission analysis, while most existing evaluation methods for energy-retrofitting have not accurately taken into account the influences of flow temperature patterns of different low-temperature heating (LTH) radiators to operational energy. In addition, comprehensive environmental impact analyses by energy systems, as well as the contributions to indoor air quality (IAQ), have not been fully achieved. Moreover, critical mapping of the sustainability of energy-efficient retrofitting have not yet been done. This omission leads to inaccuracies and misleading estimates of the benefits of LTH retrofitting from system and primary energy perspective. In order to fill these knowledge gaps, the present study evaluated two types of LTH systems combined with ventilation retrofitting, namely heat recovery jointed ventilation radiators (VRs) and baseboard radiators (BRs). A typical Swedish multi-family house was selected for retrofitting practice. This study aims at evaluating ventilation heat recovery jointed low temperature heating (VJLTH) retrofitting on energy conservation, environmental impacts and indoor air quality (IAQ) in typical Swedish multifamily houses. The compatibility of building performance and sustainability contributions were critically analyzed by delivered/primary energy usage, life cycle assessment (LCA), and IAQ modeling. IDA ICE (indoor climate and energy simulation program), SimaPro (LCA environmental impact modeling program), analytical model and on-site measurement data provided by both radiator and heat pump manufactures were employed. The results showed that the studied VJLTH retrofitting can save up to 55% of the final energy. And the corresponding primary energy savings are more than 25%. Compared with conventional radiators, low-temperature heating radiators can improve the COP by 12 &minus; 18% for air-source heat pumps. The studied retrofit can positively contribute 11 of 16 environmental indicators, 7 of which had environmental impacts reduced by more than 50%. However, neglecting the indicators with negative impacts will increase the risk of over-representing the environmental contributions. The sustainability improvements of retrofitting, particularly for future large-scale implementation, should be critically evaluated from a broader perspective than final energy savings.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
retrofitting; low-temperature heating; energy conservations; environmental impacts
National Category
Building Technologies Energy Systems
Research subject
Energy Technology; Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-183379 (URN)10.1016/j.enbuild.2016.02.050 (DOI)000376697400023 ()2-s2.0-84959922969 (Scopus ID)
Note

QC 20160316

Available from: 2016-03-08 Created: 2016-03-08 Last updated: 2017-11-30Bibliographically approved
5. Low-temperature heating in existing Swedish multifamily houses: an assessment of the significance of radiator design and geometry
Open this publication in new window or tab >>Low-temperature heating in existing Swedish multifamily houses: an assessment of the significance of radiator design and geometry
(English)Manuscript (preprint) (Other academic)
Abstract [en]

This study evaluated the impacts of radiator designs and geometries. The aim was to map the thermal  efficiency and performance differences of studied radiator types. A typical Swedish low-rise multifamily house was selected to present the analysis. Swedish climate was employed to evaluate the applicability. On-site measurements, analytical model and real-life performance data from radiator manufactures were applied for the modeling work.

It was found that radiator Type 21 1.2m x 0.4m shows the highest exergy efficiency. Type 11 1.2m x 0.45m shows the lowest exergy efficiency. There is no evidence found that Type 22 (adding more convector plate) has higher thermal efficiency than Type 21, from an engineering perspective, under the climate range of -20  to 15 . Baseboard radiator showed 34 % higher exergy performance than the most efficient conventional radiator, with the same surface area, at mean outdoor temperature during an average heating season in Sweden (-1.3 ). The results also suggest that Type 21 would have higher efficiency compared to Type 11 during 50 % time of the heating season, in severe climate conditions. In the climate of Stockholm, this was 20 %. For the mild climate, Type 11 and Type 21 perform almost the same during the whole heating season. 

Keyword
Radiator, design and geometry, low temperature heating, thermal efficiency, existing Swedish multifamily house
National Category
Building Technologies
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-193103 (URN)
Note

QCR 20160929

In press, special issue of CCHVAC 2015

Available from: 2016-09-28 Created: 2016-09-28 Last updated: 2016-09-29Bibliographically approved
6. Low-Temperature Heating with Heat Pumps in Single Family Houses: Design Requirements and Future Perspectives
Open this publication in new window or tab >>Low-Temperature Heating with Heat Pumps in Single Family Houses: Design Requirements and Future Perspectives
(English)Manuscript (preprint) (Other academic)
Abstract [en]

This study explored the potential of low-temperature space heaters connected to a heat pump in single-family dwelling in a broader context. The aim was to map the parameters that have the greatest impact on the thermal performance of this type of heating systems and their CO2 emissions. The results suggest that the ability of a heating system to be operated with a low-temperature supply depends to a large extent on the heating demand of a building, and the size, type and efficiency of the space heaters.It was shown that an increase in the water flow rate from 0.01 to 0.05 kg/s would significantly increase the heat outputs from analyzed heating systems. Consequently, this would also improve the efficiency of closed-loop heat pumps connected to these systems. This change would not increase the pumping power need, nor would it create noise problems if the distribution pipes and thermostatic valves were properly selected. It was further demonstrated that the efficiency of the heat pumps could be additionally improved by halving the energy needs for the domestic hot-water and circulation pumps. The results also suggest that the exergy need is significantly lower in heating systems that are operated with small temperature drops.

Keyword
Low-temperature heating, Energy efficiency, CO2 emissions, Heat pump, Hydraulic losses, System analysis
National Category
Building Technologies
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-193104 (URN)
Note

QC 20160929

Submitted

Available from: 2016-09-28 Created: 2016-09-28 Last updated: 2016-09-29Bibliographically approved
7. Performance analysis of low temperature heating in retrofitting practice of existing Swedish multifamily houses: An investigation including simulation and measurements
Open this publication in new window or tab >>Performance analysis of low temperature heating in retrofitting practice of existing Swedish multifamily houses: An investigation including simulation and measurements
2015 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Two types of low-temperature heating (LTH) radiators (ventilation/ baseboard radiators) are evaluated with respect to conventional radiator (high-temperature) based on simulation and measurements in retrofitting existing Swedish multi-family house. The flow temperature variations of LTH are found and the influences to COP of heat pump are quantified. The primary energy savings by retrofitting conventional to ventilation/baseboard radiators are 12.4 and 10.2 %, respectively. 

Keyword
Retrofitting, Low temperature heating radiator, Flow temperature pattern, Heat pump, Energy savings
National Category
Building Technologies
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-168713 (URN)
Conference
The 8th International Cold Climate HVAC Conference, Dalian, China, October 20-23, 2015
Note

Topic 7. Sustainable and advanced built environments

QC 20160107

Available from: 2015-06-08 Created: 2015-06-08 Last updated: 2016-09-26Bibliographically approved

Open Access in DiVA

fulltext(1794 kB)168 downloads
File information
File name FULLTEXT02.pdfFile size 1794 kBChecksum SHA-512
521df2e09f31a0012451fe13d94799af4d8778dc48bf626c4dea903567c320514699ae97f26b902444cb4ebfb071af104bd4088e8e7b30b150f0fcefd622f574
Type fulltextMimetype application/pdf

Authority records BETA

Wang, Qian

Search in DiVA

By author/editor
Wang, Qian
By organisation
Fluid and Climate Technology
Building Technologies

Search outside of DiVA

GoogleGoogle Scholar
Total: 168 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 494 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf