Ventilation for Zero Carbon Construction

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Ventilation for Zero Carbon Construction
LEaf 24/01/08
Innovation in Ventilation A Cambridge
University Start-up Company
Dr Mike McEvoy Dwell-Vent Ltd
7 Rokesly Avenue,
London N8 8NS Tel [phone] Email
info_at_dwell-vent .com Web www.dwell-vent.com
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Background
Dwell-Vent is alone in being energy efficient
whilst providing the good indoor air quality that
is a particular concern for dwellings that have
been built to be air-tight.

• The Dwell-Vent system was first researched at
  Cambridge, over a number of years, it is a
  completely passive method of house ventilation
  with heat reclaim that is directed towards the
  changing regulatory framework in Europe.
• A number of natural and mechanical technologies
  are currently available, among them
• Mechanical Ventilation Heat Reclaim (MVHR).
• Trickle vents within windows and extract fans in
  kitchens and bathrooms.

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Dwell-Vent Components

• The Supply Air Window
• Air is drawn through vents at the bottom of the
  outer pane, it is warmed as it rises within the
  cavity, by solar gain and heat reclaim from the
  room, entering the room pre-warmed through vents
  at the top of the inner window.
• Non-return valve and self-regulating vents.
• Low-E coating to the inner pane restricts
  radiative heat loss.
• Passive Stack Vents (PSV)
• Air is pulled through the window by the pressure
  induced by the PSV.

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Air Tightness and Health

•  
• Dwell-Vent needs airtight construction. 3 m3/m2hr
  (around 3ach at 50 Pa), is an optimal figure for
  Dwell-Vent, and a clear future target for
  regulations since according to the BRE most
  airtight domestic and non-domestic buildings,
  using normal (but carefully executed)
  construction methods, can have an air
  permeability down to around 3 to 4 m3/m2hr at 50
  Pa.
• A house that air-tight, without an engineered
  ventilation system, would be like living in
  inside a sealed plastic bag. Dwell-Vent
  prevents the familiar build-up of condensation,
  mould growth and particulates associated with
  sealed properties and poor health.

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Experimental Work

• Early tests were carried in a test cell - a
  highly insulated room that is fitted with
  monitoring devices to measure energy input and
  loss through windows.
• This shows how the effective U-value altered
  throughout the day. As solar energy enters the
  room the U-value becomes negative. The supply
  air window pre-heats the incoming air thereby
  avoiding draughts.
• At night the window reclaims heat escaping from
  the room and its U-value doesnt rise above 0.6
  W/m2K.

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Findings

• The optimum energy efficiency of the window
  depends on the air flow being smooth and laminar,
  which is a function of the gap width.
• The flow can be disrupted by the excessive air
  speeds resulting from wind pressure so Titon
  pressure-regulating vents are used.
• The first time supply air windows were combined
  with a passive stack vent was from the back of a
  test cell at the BRE.

• This work led to an EU funded project to install
  windows in Ireland, Poland and Denmark which
  established the range of climates to which the
  Dwell-Vent system is appropriate.
• The window design has now developed into the
  production windows being made by Howarth Timber
  Windows Doors Ltd.

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EU funded Demonstration Project

• The Danish properties were new build single
  storey family houses forming part of a semi-urban
  development.
• The Polish properties consisted of 3rd storey
  small neighbouring flats in a large new block in
  a semi-rural area.
• The Irish houses were existing 1960s two storey
  semi-detached houses on a suburban housing
  estate.

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Summary Results
Results from Denmark

• Ue -values (a measure of total energy balance)
  vary depending on flow rates, window construction
  and solar radiation.
• Average wintertime Ue-values for the three
  countries (Poland /Denmark tripled glazed,
  Ireland two panes only) were

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Simulation Results Hansard Road

• A pilot study was carried out in Norwich. Two
  houses were completely equipped with the
  Dwell-Vent system, their performance was
  monitored and reaction sought from the users.
• The predicted flow rates delivered by the PSV
  system were as shown on the graph.

Window Ue values
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Carbon Trust Project

• Our recent project, funded by the Carbon Trust,
  is the largest UK installation to date (20 units
  in Norwich/East Dereham), that has allowed
  Dwell-Vent to be evaluated across a range of
  different lifestyles, and has contributed to the
  database within the software.
• Howarths have finessed the design of the frames
  to slim sections made from laminated Baltic
  timber from sustainable sources. The windows
  have been extensively tested including for
  secured by design.

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The Final Product

• A three light window being installed at Cadge
  Road, Norwich.

• Here are the completed windows made by Howarths
  showing the windows opened for summertime
  ventilation and with the catches securing the two
  sashes released for cleaning.

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Carbon Trust Project Results
Window installation at Easton Mews, Leixlip nr
Dublin
The extent of energy saved at the Norwich test
sites was compatible with the results predicted
by simulation modelling
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Dwell-Vent-summer

• Dwell-Vent-summer provides boosted summertime
  airflow without the use of mechanical
  ventilation.
• The full system will be applicable to building
  types that tend to overheat such as offices and
  schools, as well as housing.
• It combines a new type of solar panel (made by
  Viridian Solar) and passive stacks for improved
  year-round ventilation efficiency due better
  summer airflow and enhanced heat reclaim in
  winter.

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Dwell-Vent-summer
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Dwell-Vent website
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The Dwell-Vent Advantage

• Dwell-Vent is a whole house ventilation system,
  it requires air-tight construction, optimally 4
  ach or lower when pressure tested at 50 Pa, if so
  Dwell-Vent can achieve
• Energy efficiency
• Economical heat reclaim
• Very low window U-values
• Healthy indoor air conditions
• Low tech simplicity assured by research
• Durability
• Minimal maintenance
• Draught free pre-heated ventilation
• Quite operation and noise exclusion

Mater Orchard - Dwell-Vents first installation
in Ireland