Mads Mysen

Demand controlled ventilation for office cubicles—can it be profitable?

In an office building fresh air is normally provided by ventilation systems designed for a constant air volume (CAV). This implies that for much of the time, considerable amounts of energy can be wasted on ventilating empty offices. We have performed a simple analysis of the potential profitability of demand controlled ventilation (DCV) on a reference office building in Norway. Our calculations suggest that the maximum profitable investment in DCV equipment is about 400 EURO per cellular office if central installations and technical areas can be reduced as a consequence of DCV. Reduced energy costs alone will cover an investment of about 300 EURO per cellular office. If the electrical energy price in Norway increases to the same level as in Denmark, reduced energy costs alone will cover an extra investment of about 700 EURO per cellular office.

Comparison of Two Ventilation Control Strategies in the First Passive House Standard Norwegian School

Abstract The perceived indoor climate resulting from two ventilation control strategies was evaluated in a classroom of the first school built according to the Norwegian passive house standard. Both strategies consisted of varying the ventilation rate according to room demand, ie. Demand-Controlled Ventilation (DCV). The existing strategy consisted of varying the ventilation rate in order to maintain a constant carbon dioxide concentration of 800 ppm in the classroom (constant-CO2 control). A new strategy was implemented which consisted of a combined CO2 and temperature control, ie. to control towards a proportionally lower CO2 concentration when the indoor temperature increases. The aim with this strategy was both to address overheating and the fact that perceived indoor air quality decreases when temperature rises. Indoor climate measurements, as well as questionnaires on the perceived indoor air quality and thermal comfort (completed by the pupils), were used to compare both strategies. An acceptable perceived indoor climate was reported for both strategies, with a slight improvement for the combined CO2 and temperature control. The data from the questionnaires were then analyzed using a random effect linear regression model. The regression analysis revealed that the combined CO2 and temperature control reduced the discomfort by variations of the indoor temperature significantly compared to the existing strategy (constant-CO2 control). If correctly implemented, combined CO2 and temperature DCV therefore appears to be a relevant solution for schools built to passive house standard.

VOC emission rates in newly built and renovated buildings, and the influence of ventilation – a review and meta-analysis

ABSTRACT Few field studies have evaluated ventilation strategies, such as temporarily increasing the ventilation rate, to counter the high pollutant-load from off-gassing of volatile compounds from new materials in these buildings. We reviewed longitudinal studies that measured both ventilation rate (i.e. fresh air change rate) and airborne concentration of total volatile organic compounds (TVOC). Rates of emission of TVOC follow a multi-exponential decay trend over time after completion of a building. A tri-exponential trend-was fitted by quantile regression. Although the ventilation rate is key to controlling airborne concentrations, it does not noticeably influence TVOC emission rates. Specifying low-emitting materials, or bake-out before occupancy, both have a significant impact on emission rates . The results can be used to assess and size energy-efficient practical ventilation strategies (such as demand-controlled ventilation) to keep the concentration of TVOCs within acceptable levels during hours of occupancy after completion of a new or renovated building.