Passivhaus Projects and Benefits Andrew T. Arthur MPH CMCIEH Arthur Associates
Passivhaus not Passive House Need to make distinction between: this and this
Passivhaus Standard which was developed in Germany by Dr. Wolfgang Feist of the Passivhaus Institute in Germany in the 1990's Very high standards of thermal insulation Extremely high performance windows and doors High levels of fabric airtightness Thermal bridge free construction MVHR system with high efficiency heat recovery
Core Focus Dramatic reduction of requirement for space heating and cooling, whilst also creating high indoor comfort levels Achieved primarily by: Fabric first approach to design
The Passivhaus - Definition A Passivhaus is a building, for which thermal comfort can be achieved solely by post-heating or post-cooling of the fresh air mass, which is required to achieve sufficient indoor air quality conditions without the need for additional recirculation of air
What this means is: Heat requirement reduced to the point where a traditional heating system is no longer considered essential Cooling is minimised by the same principles and by using shading and in some cases by precooling the supply air Night purging and use of natural crossventilation by opening windows is encouraged during the summer months
Design Do not conform to any one design style
Design Or any one form of construction
Basic principles: Specific Heating Demand <= 15kWh/m2/yr. (or) Specific Heating Load <= 10W/m2 Specific Cooling Demand <= 15kWh/m2/yr. Specific Primary Energy Demand <= 120kWh/m2/yr Airtightness <= 0.6 ach @ 50 pascals (n50)
Renewables Not necessary to have renewables in design but Primary energy demand of 120kWh/m2.yr difficult to achieve if buildings use direct electricity for space or water heating because of the high carbon content of UK generated electricity
Guideline targets: To achieve space heating requirement of 15kWh/m2/yr. : Recommended opaque fabric U-values of <= 0.15W/m2K U-values for windows and doors (for both the frame and glazing) need to be <= 0.8W/m2K (0.85W/m2K installed) Thermal bridging ideally needs to be eliminated or minimised, a Psi value of <0.01W/m2K is considered thermal bridge free An air pressure test must result in an n50 airtightness level averaged over pressurisation and depressurisation Whole house mechanical ventilation with heat recovery (MVHR) that is 75% efficient or better, with a low specific fan power
PHPP
PHPP PHPP incorporates the energy specifications for quality approved Passivhaus buildings and contains a series of tools for: Calculating energy balances Designing comfortable ventilation Calculating the heat load, and Summer comfort calculations
Design approach: Many factors influence approach Key early decisions need to be made Siting Orientation Building form Fenestration Hence recommendation that design is modelled using PHPP as early as possible Important for form-factor ratio, the ratio of external envelope compared to usable internal building area, is as low as possible
Design approach:
Some comparisons: Passivhaus specification for energy performance higher than Building Regulations Although PHPP is much more rigorous than SAP, we still have to use SAP for Building Regulation purposes Building Regulation air tightness requirement, worst air tightness test result allowable) is 10 m3/(m2.hr)@50pa, measured differently but PH standard is substantially higher Certified Passivhaus buildings undergo a rigorous quality control process to ensure the building will perform as designed, whereas, it is generally accepted that in terms of thermal detailing, there are very often substantial differences between design and as built details
A look at some Passivhaus buildings in Wales (1)
A look at some Passivhaus buildings in Wales (2)
This one isn't completed yet!
This one isn't completed yet!
This one isn't completed yet! Design now incorporates 6kW PV array under G59 approval of DNO primarily for heating water No wood stove for a number of reasons
This one isn't completed yet!
Questions?