Download Whole House Ventilation

Whole House Ventilation
Why do we need ventilation?
Building regulations require a minimum rate of ventilation equivalent to
one air change for the whole building every two hours.
General improvements in house construction, building regulations and
much higher levels of insulation in modern dwellings mean that houses
are becoming almost airtight. Consequently, the air inside becomes stale
with a build up of moisture and smells. The moisture can result in
condensation and mould, and a generally ‘stuffy’ atmosphere.
What types of ventilation are available?
1) Single room extractors
Traditionally, ventilation has been provided by individual extract fans
fitted to bathrooms and other ‘wet’ rooms. These provide short term
ventilation, usually very noisily. The extracted air is replaced by fresh air
entering the house through trickle vents in the window frames. These are
neither attractive nor particularly sensible (having spent a lot of money on
a well insulated house with high specification double glazing, a hole is
made in the window frame in order to create a draught!)
2) Central Extract Ventilation
As modern houses have more wet rooms, so it becomes more
economical to replace several individual extractors with one Central
extract ventilation unit. With a CEV unit, only one vent to the exterior is
required (via wall grill or roof vent) in order to expel the stale air & only
one electrical connection with the obvious savings in installation costs
over individual extract fans.
The extract unit is usually
placed in the loft or a
cupboard.
The (warm) stale air from the wet
rooms & the (cold) fresh air from
the exterior both pass through a
heat exchanger, in opposite
directions & without mixing. The
heat contained in the extract air is
transferred to the incoming fresh
air, which is introduced back into
the living areas of the building.
Heat Recovery Ventilation does
not produce heat, but minimises
the amount of heat which would
otherwise be lost through
ventilation, with degrees of
efficiency varying between 70 97%. In doing so, it reduces the
amount of heat that needs to be
produced to keep a house warm.
Heat Recovery Ventilation systems are designed to run continuously,
virtually silently, providing clean fresh air throughout the building. Normal
operation is at a very low speed, allowing the gentle movement of air
from dry rooms to wet rooms and then to the exterior. Heat recovery units
have two or more speed settings so that larger quantities of air can be
extracted as the need arises. Depending on which system is chosen,
humidistats, digital programmers, CO2 sensors and timers can also be
used to control the ventilation.
Heat Recovery Ventilation offers
the added bonus of filtering the
incoming air so that there is less
dust internally (and therefore less
dusting to be done).
Pollen filters are available, which
is a real boon to those who suffer
from allergies, asthma and hay
fever.
An HRV system can also be used
to extract air from rooms which
get uncomfortably warm ( garden
or sun rooms, kitchens with range
cookers, etc.) and redistribute the
heat from this air, via the heat
exchanger, to other rooms which
are not so warm.
Heat Recovery Ventilation
Why every home should have Heat Recovery Ventilation
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Prevents condensation and mould by removing the moist air from wet areas such as
bathrooms, kitchens and utility rooms.
Reduces the humidity so carpet and dust mites don't breed - a great help for those
with asthma and other allergy sufferers.
No draughts
Up to 95% of the heat is recovered from the air extracted (from the wet rooms) to
warm the incoming fresh air. (This feature can be switched off in the summer months
as required)
No need for unsightly trickle vents on windows
How does it work?
Heat recovery ventilation is basically the same as central extract
ventilation but instead of the air entering the house via trickle vents in the
windows, a second fan draws fresh air in and passes it through a heat
exchanger and then sends it to the dry rooms in the house. Ideally the
central unit will be sited in the roof space or garage or a cupboard.
Flexible ducting in the ceiling void runs from this unit to each wet room,
extracting the stale air, and to the dry rooms supplying fresh air. The
extractor will provide a continuous low rate of air change, giving a steady
flow of air throughout the house.
What Heat Recovery Systems are available?
CVC Direct supply a number of different Heat Recovery Units, the three
most popular ranges being the AKOR, Itho and the Ubbink
equipment.The Akor HRI is a high volume French system with a 70%
efficiency. It uses flexible ducting which makes the installation easier. It is
also one of most economical systems available. The Ubbink range of
high efficiency units uses rigid ducting (although semi-rigid or flexible can
be used). The Ubbink range is made & tested in the Netherlands, and is
probably the most efficient range of heat recovery units on the market
(quoting from Ubbink).
Helpful tip: If you are building a new house,
then we strongly advise that you make
provision for ducting the ventilation
system to the exterior while the the
building is under construction. This greatly
simplifies the installation of this item, as it
avoids having to cut a 150mm hole in the wall
at a later stage, and probably when the
scaffolding has been removed. There are 3
common ways to do this.
1. Build the wall vent grill and a short
length of 150mm rigid duct into the
wall as it is being constructed.
2. Fit the vent grills into the soffit board
with a length of flexible ducting
3. Alternatively, fit a roof vent tile, with the
appropriate connection, to the roof
while it is being tiled. The roof vent is
normally a spigot with a coloured cowl
on top and 500x500mm lead skirt.
Cowl available in Terracotta
(orange/red), Red (brick red) Sepia
(brown) and Charcoal (dark grey)
Wall grills, ducting and roof vent tiles are
available separately from CVC Direct.
Roof vent tiles are available as a special
order to match specific types of tile. Send
details of the tile to be used.