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By Bruce Marshall, Emerson Swan
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heating a home today compared to the early
’80s, homeowners are still very interested
in energy efficiency. We have boilers and
furnaces capable of pushing 95 percent
efficiency rates and considerably higher
insulation R values.
Add to this the ever-increasing aware-
ness of indoor air quality, and we have an
excellent selling opportunity for both new
construction and the retrofit market.
Today’s homes are built to promote
energy efficiency. We can’t live without air,
and lots of it—clean fresh air full of life-
giving oxygen. Yet homes built today are
constructed to keep fresh air out, all in the
name of energy efficiency.
This “air-tight” construction lowers the
heating bills, but it also restricts the flow of
fresh air into the house. The EPA estimates
the number of pollutants found in indoor
air to be as much as 70 times greater than
outdoors, even in urban areas.
An increase in the levels of pollen, dust,
insect dander, tobacco smoke and other
pollutants has been blamed for a doubling
of the incidence of asthma and allergies in
children and adults over the past 15 years.
In examining the elements of a good ven-
tilation system, it is easy to see why a heat
recovery ventilator (HRV) is the preferred
choice.
A good home ventilation system should:
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odors and pollutants.
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weather conditions.
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out of the house.
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HRVs do all these things very well, but
more importantly, do them in a cost effec-
tive way. They can transfer up to 85 percent
of the heat from the outgoing air stream to
the incoming air stream, thus reducing the
heat loss normally associated with makeup
air. They also are typically installed in the
basement, keeping noise transmission to a
minimum.
Heat
y
Recover Ventilators provide ben-
efits that are appealing to both the consumer
and the builder and can increase your piece
of the pie. Let’s look at what HRVs are all
about; what they do; why they are needed;
who is using them; and how you can make
money installing them.
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An HRV is basically an air-to-air heat
exchanger. It removes stale air from the
home and replaces it with fresh air. The
beauty of an HRV is in the exchange of
heat between the two airstreams. The
heat exchanger is specifically designed to
prevent cross contamination of exhaust
and supply air, but still provide for effi-
cient heat transfer to help reduce overall
energy costs. By removing stale air from
the problem spots such as kitchens and
baths and introducing fresh, tempered air
throughout, an HRV greatly enhances the
livability of the home.
HRVs are an integral part of energy effi-
cient home design. The popularity of HRVs
has grown since the ’70s, when energy costs
skyrocketed. The Vermont Energy Efficient
Home program strongly recommends the
use of an HRV in its guidelines for new
home construction. Most builders of quality
homes today will include an HRV in the
mechanicals.
Proper installation of an HRV begins
with proper design for the individual
home. The unit should be sized to meet
the exhaust air requirement and should be
balanced with equal exhaust and supply air.
For residential applications, the following
levels are recommended:
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Kitchen: 60 CFM (Cubic Feet Per Minute)
Baths:
20 CFM each
Laundry: 20 CFM
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Basement:
20 CFM
Kitchen:
10 CFM
Dining Room:
10 CFM
Family Room:
10 CFM
Living Room:
10 CFM
Master BR:
20 CFM
Bedrooms:
10 CFM each
Baths:
10 CFM each
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By adding up the exhaust requirements,
and then balancing the supply air to it, the
contractor can select the correct-size HRV
unit. This is called the room count method.
It is important to match the design require-
ments of the job to the capacity of the unit.
An HRV can be installed independently
when the home is heated hydronically, or
integrally with a forced hot air system.
Once the unit has been selected, it’s
just a matter of sizing the ductwork to the
individual rooms. There are many types of
flexible ductwork available today, and they
are ideal for this application. Installation
skills required are similar to those used
when installing a furnace, air conditioning
system or central vacuum system.
Another way to size is the whole-house
ventilation method. Using a whole-house
ventilation rate of 0.3 ACH (Air Changes
per Hour), the HRV cfm (cubic feet per
minute) needed can be determined. The
following are a couple of examples of this
calculation.
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800 sq ft X 8 ft ht. = 6,400 cu.ft
6,400 cu.ft ÷ 60 = 106 cfm
106 cfm X 0.3 ACH = 32 cfm
A unit capable of moving 32 cfm will be
adequate for this condo.
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4,000 sq.ft. X 8 ft.ht. = 32,000 cu.ft.
32,000 cu.ft. ÷ 60 = 534 cfm
534 cfm X 0.3 ACH = 160 cfm
A unit capable of moving 160 cfm will be
adequate for this building.
A Heat Recovery Ventilator will add
between $2,500 and $5,000 to the cost of
a new home. This additional cost is more
than made up for in comfort and the peace
of mind provided by knowing that the home
is free of indoor pollutants.
Of equal importance to the installing
contractor is the added profit dollars associ-
ated with the installation. When all the ben-
efits associated with an HRV are presented
properly, you will be surprised at how easy
a sell it actually is.
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