energy efficiency

The materials that compose the built environment have a key role in the resulting energy demand since their thermal properties affect the heat transfer processes. The use of cool materials aims at increasing the albedo of the urban surfaces and decreasing the heat absorbed by them. Cool materials can decrease roof temperatures, reduce energy needs for cooling and improve indoor comfort for spaces that are not air conditioned.

Green buildings incorporate several features to improve energy efficiency, indoor environmental conditions, and occupant satisfaction. However, studies have indicated that green-certified buildings do not always provide occupants with an acceptable level of satisfaction. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) requires that at least 80% of occupants are satisfied with the indoor thermal conditions.

Current building regulations are designed to ensure that buildings, including newly built and retrofitted residential dwellings, are more energy efficient. This has raised concerns and practical challenges in relation to maintaining acceptable indoor environmental and air quality. However, there are minimal data available regarding long-term indoor air pollutant concentrations in low-energy residential buildings.

This paper reports preliminary analysis from a large field study of 100 university classrooms in Central Texas. Lecture classrooms and auditoriums were sampled for three consecutive weekdays in the 2019 – 2020 academic year. Carbon dioxide (CO2) concentrations, used as a marker for both ventilation and exposure, and temperature were measured in the general room area and when able, the supply airstream. HVAC control data that relates to ventilation was also saved for comparison.

In this extended abstract, we introduce the new IEA EBC Annex on 'Energy Efficient IAQ Management in residential buildings'. In this Annex, we address a number of challenges in implementing smart IAQ management strategies. 

Annex 68 provided us with a general framework for integrated simulation and assessment of Energy Efficiency (EE) and chemical indoor air pollution. This framework can now be further extended to develop and assess a series of smart Indoor Air Quality (IAQ) management strategies. 

Ambitious goals regarding CO2 neutrality put the energy renovations of apartment buildings in the top places on the energy efficiency & sustainability agenda in Denmark. Improved airtightness and maximum primary energy requirements imply utilization of ventilation with heat recovery. The control of ventilation installed during renovations often considers a whole dwelling as one climate zone, which neglects differences among individual rooms. Increased insulation and tightness leads to higher sensitivity to solar and occupancy gains, moisture loads and pollutants.

Humidity-based DCV systems have been widely used in France for 35 years and are considered as a reference system, including for low-energy residential buildings. The on-going Performance 2 project delivers the new results of a thirteen-year monitoring in twenty-two social housing apartments. The involved consortium is composed of Cerema, Univ. Savoie Mont Blanc and two industrials partners: Aereco and Anjos. 

IEA-EBC Annex 86 “Energy Efficient IAQ Management in residential buildings” aims to propose an integrated rating method for the performance assessment and optimization of energy efficient strategies of managing the indoor air quality (IAQ) in new and existing residential buildings. Our goal is to work in an international collaboration so that the different approaches to design and operation of ventilation in different countries are accounted for.

In order to achieve nearly net zero energy use, both new and energy refurbished existing buildings will in the future need to be still more efficient and optimized. Since such buildings can be expected to be already well insulated, airtight, and have heat recovery systems installed, one of the next focal points to limiting energy consumption for thermally conditioning the indoor environment will be to possibly reducing the ventilation rate, or making it in a new way demand controlled. However, this must be done such that it does not have adverse effects on indoor air quality (IAQ).

Both new and renovated existing buildings will in the future need to be optimized in such a way that can achieve to have nearly no energy use while still providing impeccable indoor climates. Since such buildings can already be assumed to be very well insulated, airtight, and to be equipped with heat recovery systems, one of the next focal points to limiting energy consumption for thermally conditioning the indoor environment will be to possibly reducing the ventilation rate, or to make it in a new way demand controlled.