21 May 2019 Passive House kitchen extractor hood guide from PHI

21 May 2019 by Jason Quinn
For those of us designing Passive House we can all rejoice in the release of the official PHI guidance on kitchen extractor hoods and how to consider the heat losses in their use. To my knowledge there is reason to believe that a good recirculating hood can be better than a poorly performing extractor hood in removing fine particles. I’m glad we have a good guide on how to size and account for the energy loss of extractor hoods but the discussion on ‘which is better’ has not been concluded.
I’d also point out that the Swegon CASA R3 Smart MVHR, which is now available in NZ, has the ability to have a kitchen extractor and the MVHR all in one box. This is likely the most efficient way to have a kitchen extract hood and a MVHR as the heat recovery continues and the air flow stays balanced (according to the manufacturer) with kitchen hood operation. I’d like this box to become PHI certified but it can be used in Certified PH for now with conservative assumptions.
“This guide serves as a planning aid for integration of kitchen exhaust systems for energy
efficient buildings. In addition, it provides an approach for considering kitchen exhaust systems
in the energy balance calculation of the Passive House Planning Package (PHPP).”
“Recommendations for buildings with an extremely low heating demand (such as Passive House buildings)
· Preference should be given to recirculation hood systems.
· Exhaust air kitchen exhaust systems are possible. The following points must be considered:
o Solutions should be provided that ensure adequate incoming air flow. The exhaust air outlet and air inlet must be equipped with airtight seals. Non-return valves are usually insufficient.
o Impairment of comfort cannot be ruled out. Solutions must be sought which allow the introduction of incoming fresh air directly near the cooktop.
o Systems that limit the operating time and reset the maximum flow rate after a certain time interval (automatic system), should be used.
o Preference should be given to systems which ensure adequate air capture using moderate exhaust air flows. As investigations relating to the capture of fumes have shown [BewDunst], considerable differences exist between individual products. The air flows required for collecting a defined amount of fumes differ by about 60% in the
examined systems.
o In small apartments the heating demand, and also the heating load, are significantly increased due to the additional ventilation heat losses. Kitchen exhaust systems, which operate by exhausting the fumes externally, should not be used if the average size of the apartment is less than 90 m².”

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