Here's A Simple And Inexpensive Way To Get Automatic House Ventilation

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Here's A Simple And Inexpensive Way To Get Automatic House

Ventilation

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NATIONAL RESEARCH COUNCIL

CANADA

DIVISION OF BUILDING RESEARCH

HOUSING

NOTE

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WAY

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REPRINTED FROM

CANADIAN BUILDER, VOL. XIII, No.

9

SEPTEMBER 1963, p.

48

OTTAWA, OCTOBER 1963

This Note may be reprinted without amendment provided acknowledgement is given to Canadian Builder.

F I G U R E .

1

I

Here's a simple and iinexpensive way

to get automatic house venRiilaRiion

By ALAN VEALE a regular flow of heated, fresh, outdoor fiers can also be used, but they are no

Housing Section, Division of Building air to all parts of the house. Such ven- a simple solution to the condensatior Research, NRC tilators are by no means unusual, and problem. Actual humidity levels withi~ A simple and inexpensive automatic

ventilator, easily installed in most Cana- dian houses, could help greatly to re- duce the excessive humidity and con- densation which occurs in winter. The ventilator is suitable for any house with a forced warm-air furnace and consists only of a simple duct, equipped with a convenient and easily adjustable damper, running from outside the house to the cold air return plenum of the furnace. This ventilator can automatically supply

are commonly used in some parts of the Prairie Provinces.

The Condensation Problem

Many human activities, including breathing, cooking, washing, and clothes- drying add moisture to the air within houses and thus raise the humidity level. The most practical methods for reducing the humidity level in houses are to in- crease the rate of ventilation or to re- duce the sources of moisture. Dehumidi-

houses in winter depend directly on botl the rate at which moisture is added tc the air and on the rate or amount o ventilation. As both of these rates ma! vary greatly, depending on the construc tion of the houses and the habits of thc occupants, the resulting humidity level may also vary greatly from house tc house.

The high humidity that occurs i~ some houses during cold weather cause condensation on windows, with possibl~

.... i;; X . . , - C. .: ... ...

Summary

This simple and inexpensive venti- lator could benefit many Canadian homeowners and builders. It is suit- able for any house with a forced warm-air furnace and consists of a duct, with an adjustable damper, run- ning from the outdoors to the return side of the furnace blower. It could be useful in either of the following two conditions:

1-Severe condensation occurs in many Canadian homes due to limited ventilation or excessive sources of moisture, and despite all the literature

concerning control of moisture sources and increased ventilation. Dissatisfac- tion and expense result for the home- owner, and complaints are made to, or about, the builder, who is not usually at fault. This ventilator could easily alleviate these problems. Promises of freedom from condensa- tion could be a valuable sales feature for builders who install ventilators.

2-There are many homeowners who now open windows as necessary "to control the humidity and air fresh- ness" in their houses. This ventilator

would provide an alternate form of ventilation which is convenient and regular, easily controlled and free from draughts. Such features should appeal to the homeowner and thus to the speculative builder.

(Ed.-A prominent Prairie building firm, which has made a similar type of system a standard installation in their houses for seven years, states it is a valuable selling feature and that the cost of installation averages

damage to drapes and walls, and some- times causes dampness and mildew in cupboards and on some wall surfaces. There is mounting evidence that these condensation problems are the cause of serious and frequent complaints in many Canadian homes in winter.

These problems are more likely to occur in houses which are small or crowded, which are tightly built, and in which a large amount of cooking, wash- ing, or clothes-drying takes place. The ventilator described here can eliminate or greatly reduce the problems of con- densation in these homes. The simple rule of operation is that the damper should be kept open whenever there is appreciable condensation on the inside window surfaces. Home owners should still be encouraged, however, to limit sources of moisture as much as possible.

There are, of course, a great many houses in which excessive condensation does not occur during winter, due to some combination of the type of house construction and the habits of the occu- pants. In these houses, the proposed ventilator can be used as a convenient and automatic alternative to the ventila- tion normally provided by opening win- dows.

The ventilator thus eliminates the draughts due to open windows and is a very effective means for eliminating odours and controlling air humidity and freshness. The damper should be opened whenever condensation appears on the inside window surfaces or whenever fresh air is desired within the house. Those who prefer ventilation by open windows may leave the damper closed. Ventilator Design and Operation

The ventilator consists of a simple duct, which is equipped with a close-

fitting and conveniently adjustable

damper, and which runs from the out- side air to the cold air return side of the forced warm air furnace (as shown in

Fig. 1). The duct should be insulated

throughout its full length with rnoistu~e- resistant insulation unless it is so lo- cated that its low temperature and pos- sible moisture condensation and drip- ping will not create problems.

The recommended size of ventilator

duct is 5 in. in diameter. A smaller duct

would not usually provide adequate ven- tilation. If a larger duct is used, and the house occupant does not keep the damper partially closed, fuel costs could be raised unnecessarily and more ven- tilating air might be drawn in than could easily escape through the normal open- ings of a house such as the furnace chimney and cracks around windows. This would result in pressurization of the house which would tend to increase the possibility of condensation in attics and between the panes of double win- dows.

The ventilator functions exactly like

one of the cold air returns within the '

house, except that it draws air from outside. When the damper is closed, the ventilator will have no effect whatever. When the damper is open, with the furnace blower not operating, the ven- tilator will merely function as one more opening in the house walls (such as a partially cpen window or a crack under the door). Because any air which flows in through the ventilator duct is dis- tributed among the many air outlets within the house, it should not cause draughts as would an open window, and it will tend to ventilate all rooms equal- ly. When the damper is open and the furnace blower is operating, fresh out- side air will be drawn in through the ventilator, heated by the furnace, and distributed throughout the house.

Completely automatic ventilation can be obtained, at an increased cost for equipment, by means of a humidistat which automatically controls the posi- tion of the damper. This type of system is currently being tested by the National House Builders Association Research Committee in their Mark 111 house.

Builders could benefit in two ways by installing a ventilator of this type in all their new houses. Firstly, it could be a valuable sales feature. Its effectiveness in providing humidity and odour con- trol, its ability to provide regular amounts of ventilation without draughts, and its convenience of operation and control, are advantages for the home- owner. Secondly, the ventilator should prevent customer complaints of conden- sation problems. These complaints are seldom the fault of the builder, but are difficult to answer, particularly when

complainants had no trouble in former

houses. Homeowners are more likely to heed advice to keep the ventilator open than advice to open windows because the ventilator is convenient, causes no draughts, and is a less obvious source of heat loss than open windows.

A prominent Prairie building firm re- ports that a fresh-air intake in the forced warm-air heating system has been a standard installation in all their homes

built since 1956 and that it is a positive

and permanent means of preventing con- densation due to excessive relative hu-

midity during cold weather.

-

They state that, "The installation is very simple, consisting of a 5-in. round duct from the outside of the foundation wall leading directly to the return air plenum as close to the furnace as pos- sible. A manual damper is installed in the duct on the inside of the wall and a grille and fly screen are installed on the outside wall flush with the exterior fin- ish material."

They report that the entire length of the duct is insulated on the outside surface to prevent excessive condensa- tion on the cold surface of the pipe. They also report that the cost of the installation averages ten dollars per unit including labor and that this inexpensive ventilator, if properly demonstrated to a potential purchaser, can be a valuable selling feature.