Wednesday, 25 May 2016

Sherwoods Passivhaus low energy engineering review on site


We recently visited one of our Passivhaus schemes to review how the build was coming along on site and also inspect the M&E systems prior to cover up.  The scheme, called Sherwoods, has benefited greatly from our integrated design approach.  For this scheme we were able to bring all our design disciplines together in an integrated way - architecture, Passivhaus design, healthy building design, low energy engineering and permaculture.    


Sherwoods under construction

On the M&E side of things the aim was to integrate small and simple systems within the Passivhaus design and to do so following healthy building design principles.

Designing in small and elegant heating solutions for homes that do not require much heat can be challenging.  Most systems on the market such as biomass and heat pumps systems linking into underfloor heating are simply too costly and too over engineered in a Passivhaus.  The right balance we found with this scheme was a small log burner, which will be inset into masonry, with back boiler feeding into a thermal store.  The thermal store was sized appropriately to match the back boiler output and serves the clients hot water and small heating need without being over engineered.  Back up is via electric immersion which is modulated in output to suit the electrical load being generated by the PV array on the roof.  We then arrived at a rather elegant, simple and small wall heating solution in some of the perimeter rooms which is fed from the thermal store.  Wall heating systems are considered even more effective than underfloor heating at delivering comfortable and radiant heat and they can be down-sized to suit the heat loss requirements for each room, hence can be compact and small.  Underfloor heating typically fills the whole floor which becomes a costly system in a home that does not need much heat.   

Wall heating system
Thermal store installation

We also designed the mechanical ventilation with heat recovery (MVHR) system where we are distributing air via a radial ductwork system to floor and wall grilles.  The idea here being to provide optimum routing of air from low level to high improving the overall comfort experience.  Incoming fresh air is via an earth tube primarily because the house is built into the earth. 


Supply & Extract plenums
Neatly installed and well insulated duct and pipe services


The services installation is by a company called Go Green Engineering who have worked closely with us to ensure services are installed in accordance with our design, are fully insulated and adhere to the strict air tight criteria where they penetrate the fabric.

Services air tight penetration seal

In addition to designing mechanical services for optimum radiant and air quality comfort we also designed the electrical systems to limit electric magnetic radiation (EMR) in the home, which is another healthy building design principle.  

The clients themselves, who were fully involved in the design journey, will be sourcing their own managed wood on their permaculture site to fuel the wood burner.   

For more details on our low energy design service visit our expertise page 



Sherwoods with its lovely green roof coming along nicely
Sherwoods timber cladding







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