Passivhaus Consultant and Designer, Bristol.  Very Low Energy Buildings.  Domestic and non-domestic.  New build and refurbishment. 

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Bristol, UK


Entries in Airitghtness (10)


Indoor air quality in the news and blogosphere - what's the answer?

The Guardian and Sustainable Homes blog have both recently published pieces about indoor air quality and energy efficiency.  Both articles highlight that increased energy efficiency is linked with poorer indoor air quality which is associated with health problems, particularly asthma.  The issue arises as more energy efficient buildings are designed and constructed with higher levels of air tightness.  This means that air cannot leak through cracks and gaps in the building fabric to refresh the internal air with air from outside.

However, the air we breathe and the fresh air which flushes out contaminants from your house are not supposed to be replaced by flow through gaps in the fabric, the fresh air is supposed to be drawin in through background ventilators, usually trickle vents in windows, by extract fans in kitchens and bathrooms.  The problem is that the trickle vents are often not sufficiently large and the extract fans are set on low speeds to avoid noise.  With increasing airtightness the gaps in the building are not there to provide a safety net.  There is also a problem when the fans are off, when wet rooms are not in use.

One answer is to use continuous fans which run quietly and continuously at a background speed and then increase the speed to purge ventilate when bathrooms and kitchens are in use.  This can provide sufficient ventilation, but it also purges heat from the builidng.

The best solution - well designed, high quality, silent, heat recovery ventilation (HRV) - such as this unit at Toronto Road, Bristol.  Come and see it on Saturday 26 September when it is open for Bristol Green Doors.

Ventive is an innovative alternative which can be installed in chimneys as part of a refurbishment, with less disruption than full HRV. 


Reedley Road - performance gap eliminated

Predicted specific heat demand 36 kWh/m2/yr.  Actual specific heat demand 24.5 kWh/m2/yr.

This Passivhaus inspired refurbishment project exceeds the design expectations with over 80% of the heating provided by a wood burner in the kitchen/living area.   The specific heat demand is just below the threshold for the Passivhaus refurbishment standard EnerPHit.

Come and see it at Bristol Green Doors 26 September 2015. 

Reedley Road Design Stage PHPP Modelling



Ancre Hill Winery - new straw bale winery building going up 

Ancre Hill Estates is an organic winery in Monmouth specialising in quality sparkling wines made in the champenooise style.

We have been helping them with energy aspects of the design of their new winery building where wine will be made, aged and stored.  

The new building is a steel portal frame farm building with straw bale walls and sedum roof. Attention has been paid within the design to making the building airtight and thermal bridge free.

The building has specific temperature requirements in different rooms and at different times of year.  

To  minimse energy use the building will have no heating or cooling systems.  

Ventilation is required to remove CO2 that is generated by the fermentation process. We have been working with Green Building Store to develop a control system for the Paul Novus 450 Mechanical Ventilation with Heat Recovery (MVHR) unit, which is able to manage the CO2, maintain humidity levels and provide adequate night cooling in summer.  

The building is being built by G Adams Construction with training and supervision in straw bale construction from the Doret Centre for Rural Skills.







An air test was undertaken by John from Building Analysis and Testing yesterday at 101 High Kingsdown.  This is a 1970s refurbishment.  We were pleased with the air permeability of 2.1m3/m2/hr @50pa which beat the target of 3.  The main areas of leakage were between the ground and first floors and partition walls where we knew we had to make compromises due to access.  The result is compatible with the installed Paul Novus MVHR from the Green Building Store.



Refurbishment Works at High Kingsdown

We have been advising on an energy efficiency refurbishment of a 1970s house in High Kingsdown, Bristol. The house is to be a student let and one of the drivers for the refurbishment was severe condensation and mould which had developed during previous occupancy.  The refurbishment strategy included:

  • cavity wall insulation, internal wall and loft insulation
  • new triple glazed windows with internal blinds
  • air tightness strategy
  • new condensing gas boiler
  • mechanical ventilation with heat recovery (MVHR)

The design and implementation has been undertaken by Studio 2 a collaboration between Piers Sadler Consulting, S2 Design Architects and Greenheart Sustainable Construction all based at Studio 2, St Andrews Road, Montpelier, Bristol.

The construction work is well under way with insulation, airtightness and MVHR installation almost complete. Piers Sadler Consulting has been advising on some of the complex detailing for air tightness and thermal bridge avoidance as well as on MVHR design and procurement.

Paul Focus 200 with insulated supply and exhaust ducts and frost protection shown below: