PhD

PhD

COMBINING BUILDING AUTOMATION CONTROL SYSTEMS WITH ENVELOPE RETROFITTING TO IMPROVE THE ENERGY PERFORMANCE OF COLD CLIMATE HOUSING

DATE : AUGUST 2016 РAUGUST 2020

ABSTRACT

Improving the energy efficiency of buildings by combining envelope and energy systems retrofitting with smart technologies is recommended by the Energy Performance of Buildings Directive. The largest share of the existing building stock consists of residential buildings, so retrofitting these is essential to reduce the energy consumption of the building stock. Retrofitting projects and research studies of dwellings have mainly focused on improving the performance of the thermal envelope and systems, while smart technologies, such as building automation control systems (BACS), are not often used to their full potential. There are only few studies that estimated the potential energy savings from implementing BACS in residential buildings. They demonstrated that significant energy savings were achieved and that the energy label of the building improved. The literature also showed that the effect of BACS was higher when the original delivered energy was higher. Most of these studies focused on warm climates and the knowledge on the impact of BACS as retrofitting measure in cold climates is limited. This thesis evaluates the impact of combining building automation control systems (BACS) with envelope and energy systems retrofitting for residential buildings in Norway.

An analysis of the building stock and of the literature was conducted to investigate the retrofitting status and typical energy consumption of residential buildings in cold European climates and specifically in Norway. Based on this analysis, two typical building typologies that represent a large number of buildings and a large share of the total energy consumption were chosen, i.e. a detached single-family house and an apartment block. Building performance simulation models of these building typologies were created in IDA-ICE. The descriptions of BACS measures given in the building automation standard EN 15232 were used to define relevant BACS for the case study buildings. As the standard can be interpreted in different ways, two approaches were used to illustrate the impact of system design and choice of setpoints. The impact of BACS as individual retrofitting measures as well as in combination with building envelope and energy systems retrofitting was assessed. Optimal retrofitting combinations were also found, using IDA-ICE with GenOpt. The results were assessed in terms of achieved energy savings, cost-effectiveness and thermal comfort.

It was found that the energy consumption was reduced by up to 24% when BACS were implemented as a retrofitting measure. Heating control strategies had the largest impact on decreasing the energy consumption. The other control strategies did not individually improve the energy performance of the buildings, though most energy savings were achieved when all control strategies (i.e. heating, lighting, ventilation and shading control) were combined. The energy saving potential depends highly on the system design and choice of setpoints. When BACS were combined with envelope and energy systems retrofitting, energy savings up to 57% and 46% were achieved for the detached single-family house and apartment block, respectively. Installing an air source heat pump was the most effective retrofitting measure. Upgrading the heating and lighting control strategies was essential for cost-effective retrofitting. The control strategies for ventilation and blind control did not affect the energy consumption, but the latter improved the thermal comfort by reducing the number of overheating hours. The results showed that BACS had a bigger impact on more compact buildings, such as apartments.

To conclude, BACS has a significant energy saving potential in residential retrofitting projects. The impact of BACS on the energy performance increased when the building was more compact. Its impact was lower than that of building envelope and energy systems retrofitting measures, though large enough to be an attractive retrofitting measure when other measures are challenging. Combining BACS, especially heating and lighting control strategies, with a high-performance building envelope resulted in the highest energy savings and was the most cost-effective. When a deep retrofit of the building envelope is not possible, high-performance BACS are an attractive and profitable retrofitting measure.

OBJECTIVES

The ambition of this thesis is to contribute to energy-efficient retrofitting of the Norwegian residential building stock. For this purpose, the main research question is defined as: What is the impact of integrating building automation measures with envelope retrofitting on the energy performance of housing in Norway?. The research question is divided into the following sub-questions:

  • What is the current status of the housing stock and of retrofitting in Norway?
  • What are the energy performance characteristics of a typical Norwegian house?
  • How can an energy performance simulation model of a reference building be defined, created and validated?
  • What is the effect of building automation control strategies on the energy consumption and thermal comfort of the reference buildings?
  • What are the optimal retrofitting packages for the reference buildings where building automation control systems are combined with building envelope and energy systems retrofitting?
  • What is the cost-effectiveness of optimized retrofitting packages for the reference buildings where building automation control systems are combined with building envelope and energy systems retrofitting?
METHODS
  • Literature review
  • Energy performance simulations
    • Model validation
    • Creating custom control strategies
  • Estimating energy savings from building automation control systems
    • Simple factor method
    • Detailed calculation method (energy performance simulations)
  • Single-objective optimizatiom
  • Thermal comfort assessment
    • Annual discomfort hours
    • Indoor discomfort degree hours
  • Economic assessment
    • Discounted payback period
    • Life cycle cost assessment