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 Ventilation (5)


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. 


Commissioning MVHR at Ancre Hill Winery

MVHR Commissioning by Andrew Farr of Green Building StoreThe MVHR at Ancre Hill Winery was designed jointly between Piers Sadler Consulting and the supplier Green Building Store.  The building has no heating or cooling so the system has been designed to help maintain near constant temperatures at 10-15o C. The system is designed to remove CO2 from the building when wine is fermenting and to keep the building cool in summer.  From Autumn to late Spring the system is automatically controlled by as 0-10V signal from CO2 sensors so that the ventilation progressively ramps up as CO2 concentrations increase. In summer when CO2 is not being generated, the summer by-pass has been specially adapted to enable air as cold as 2oC to be drawn into the building at night for cooling purposes.  The automatic control is switched to manual and the fan speed adjusted to vary the cooling.  The supply air ducts have been insulated to avoid condensation.


Fungi Fruits

We are advising Fungi Fruits on simple, energy efficient ventilation approaches to manage temperature, CO2 and air quality in their mushroom growing vaults below the former Green Park Station in Bath.  We have been working with Philip Haile of Transition Bath who has undertaken a thermal imaging survey and is helping with the designs.

The vaults require warm dark conditions for incubation and cool light conditions for fruiting.  The challenge is to reject heat and provide cooling in summer whilst retaining heat and adequate ventilation in winter.  Hygiene is also critical.

The available funds are limited, so simple low cost solutions are necessary.  

The proposed solution is to separate the vaults into a number of different areas and use a combination of night cooling and evaporation to achieve suitable humidity, CO2 concentration and temperature in the fruiting vaults and to vary packing density of the heat producing incubating bags and ventilation rate to manage temperature in the incubating vaults.

This is a fascinating project and we really hope that we can help Fungi Fruits become a thriving busines in Bath producing oyster mushrooms below the old station and selling them in the farmers' market upstairs.


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.







10 things to consider when choosing between MVHR quotes

  1. Price
  2. Efficiency
  3. Specific fan power
  4. Ducting type
  5. Controls
  6. Frost protection
  7. Cold side duct insulation and airtightness
  8. Cost of filters
  9. Noise
  10. Commissioning

Look out for re-heaters too - they are a sign of inefficiency as the supply air needs to be heated on a cold day due to low delivery temperatiures from the heat exchanger.

We recently reviewed two quotes for a job covering most of these 10 and the results are below:

In this case System 1 was a Paul Focus 200.  This was more expensive but we recommended it and it has now been supplied by green Building Store and installed by Greenheart Sustainable Construction.