Method and apparatus for testing the air-tightness of a building using transient pressurization

A method and apparatus for testing the air-tightness of an enclosure such as a house or building, includes the increasing of the pressure within the enclosure relatively rapidly to above a predetermined amount with all doors and windows being closed and then measuring the leakage of decay of the increased pressure together with the time in order to arrive at a leakage coefficient of the enclosure. The increase in pressure should be high enough above atmospheric pressure to allow accurate pressure measurement, but not high enough to damage the structure.

One of the ways of improving the cost of heating an existing building such 
as a house or the like is to reduce leakage which normally occurs through 
window frames, door frames and other vents or cracks normally present in a 
building. 
However, it is difficult with present techniques to assess the efficiency 
of sealing procedures which may have been undertaken. 
Present techniques, as illustrated in the background of the art shown, for 
example, in U.S. Pat No. 3,893,332 (Dolan), U.S. Pat. No. 4,363,236 
(Meyers) and U.S. Pat. No. 3,918,291 (Pauly) and in addition in a paper 
presented by Blomsterberg appearing in Ashrae transactions 1979, volume 
85, part 1, all involve creating a steady state and then measuring the 
volume of air introduced to maintain the steady state. These techniques 
have very many problems as explained in detail in the above documents 
relating to changes in temperature, changes of volume in the structure and 
in the vessel which supplies the pressurized gas. In all these cases the 
attempt is to maintain or achieve a steady state but, of course, slight 
variations from the steady state will occur since it is very difficult to 
set up the steady state. 
These techniques are available but generally involve very expensive and 
complex equipment and hence the use and effectiveness of these techniques 
has been limited. 
SUMMARY OF THE INVENTION 
In contrast to the above techniques, the present invention provides a 
surprisingly different arrangement in which a pressure pulse is created of 
short duration. The pressure pulse is created by rapidly introducing gas 
into the structure at a rapid rate and for a short period of time so the 
pulse has a profile which rapidly rises from an ambient pressure within 
the structure to a peak and then declines back to the ambient pressure 
without at any time reaching a steady state. 
The term rapid rate as mentioned above is intended to include any rate 
which is sufficiently greater than the steady state rate, that the 
pressure within the structure rises rapidly from the ambient pressure to a 
pressure considerably higher than the ambient pressure. In the prior art 
techniques the pressure, of course, must increase at some times in order 
to provide the slightly increased pressure which is used in steady state 
but this is very different from the rapid rate in which the gas of the 
present invention is introduced. 
The short period of time mentioned above is intended to include any 
situation where the injection or introduction of gas is halted or 
controlled prior to achievement of a steady state or damage to the 
building. Firstly it will be appreciated that the above expressions define 
the creation of a pressure pulse as opposed to the conventional techniques 
wherein a steady state is created. 
In order to obtain information concerning the air-tightness of the 
structure, information concerning the profile of the pulse is obtained 
which can then be used in calculations to develop a factor for 
air-tightness of the structure concerned. 
The information detected can relate to two separate points on the profile 
and the time between those points. In an alternative arrangement the 
information can relate to the value of the peak of the pulse which can be 
combined with a value for the pressure within the vessel from which the 
gas is released prior to the release in a yet further calculation. 
With the foregoing in view, and other advantages as will become apparent to 
those skilled in the art to which this inventiuon relates as this 
specification proceeds, the invention is herein described by reference to 
the accompanying drawings forming a part hereof, which includes a 
description of the best mode known to the applicant and of the preferred 
typical embodiment of the principles of the present invention, in which:

In the drawings like characters of reference indicate corresponding parts 
in the different figures. 
DETAILED DESCRIPTION 
Proceeding therefore to describe the invention in detail, one device to 
carry out this test may consist of a pressure tank with a quick-opening 
valve which will release compressed air or other gas into the building 
together with a pressure sensing apparatus which will detect and time the 
rise and/or fall in pressure after the compressed air or gas is released. 
The compressed air or gas may be sealed in a tank by a relatively large 
diameter fast acting valve held in the normally closed position by a 
spring. The valve may be actuated by compressed air from the cylinder, 
released through a manual valve in a small air line, which the operator 
will open instantly, or it may be actuated electrically. When the house 
pressure reaches an upper limit, it will be sensed by a pressure 
transducer which will shut off the compressed air to the valve actuator 
and the spring will drive the valve closed. 
At this point, the house pressure will begin to fall and the fall past, for 
example, 200 Pa will operate an electronic timer and fall past, for 
example, 20 Pa, will stop the timer. The elapsed time will therefore be a 
measure of the leakiness of the house. 
A further method is based on the assumption that the flow rate from the 
tank will be a function only of the remaining tank pressure. Therefore, it 
will vary with time in the same way, every time a test is run. In this 
second method, the valve would be driven open at a certain time and would 
stay open. The house pressure would rise, and then fall again as the 
compressed air or gas was depleted from the tank. The time from the 
instant when the house pressure reached, for example, 20 Pa until it fell 
again to 20 Pa would be a direct measure of the leakiness of the house. 
These pressure measurements are, of course, measurement above ambient 
pressure. 
As an example of the first method, the principles of which would be 
applicable to the second method, the volume of a typical house might be 
510 M.sup.3 (18000 ft.sup.3). The pressure will be at 101 kPa (14.7 psi). 
The pressure tank may contain approximately 2.25 M.sup.3 (80 ft.sup.3) of 
air or gas (as measured at a standard temperature and pressure) and at a 
pressure which can be as high as 21 MPa (3000 psi) or less depending on 
the size of the tank used. 
This amount of air would be sufficient to pressurize a house to 450 Pa 
(0.065 psi) above atmospheric pressure, but it will be appreciated that it 
will be necessary to assure that the overpressure was not high enough to 
damage the house. 300 Pa is generally considered a safe pressure. 
A well constructed house will leak at a rate of from 1 to 4 air changes per 
hour at 50 Pa. This is equivalent to from 0.014 to 0.70 M.sup.3 per second 
(5 to 25 ft.sup.3 per second). 
Based on these leakage rates, the fall in pressure from 200 Pa (an 
appropriate trigger point at which to start an electronic timer) down to 
20 Pa, the lowest pressure at which accurate readings can be taken, would 
be from 1 to 4 seconds and this kind of pressure transient can easily be 
measured by a conventional electronic timer with two pressure transducers. 
This enables the leakage rates to be ascertained and appropriate action 
taken if desired. 
The preferred embodiment is the portable tank method described and is 
probably the most efficient and practical although other methods can, of 
course, be used. 
In FIG. 1, the preferred embodiment of the apparatus is shown in which the 
pressure tank 10 is supported upon legs 11 and is provided with a fill 
valve 12 on the underside thereof. An electronic package 13 is secured to 
the tank by mounting straps 14 and a carrying handle 15 extends from the 
package as shown. 
A conventional fast acting valve 16 is situated upon the upper end of the 
tank and controlled by a valve controller 17 operatively connected to a 
timer schematically indicated at 151 in the electronics package, and a 
bell shaped nozzle or other type orifice 18 extends from the valve 16 for 
the ejection of the gas against the convex surface 19 of a deflector held 
in a spaced above relationship to the nozzle by means of legs 20. 
The electronics package 13 includes a pressure sensor 152 which detects 
pressure values as explained previously, either in the decline portion of 
the pulse or at the commencement of the pulse and then at the end of the 
pulse, as also explained before. The pressure sensor 152 is connected also 
to the timer 151 so that the time between the points on the pulse can be 
measured. 
The fast acting valve acts as a rapid release valve so as to rapidly 
release the gas so that the pressure within the building or structure 
rapidly increases. Thus the gas is introduced at a rate which is 
considerably in excess of any leakage. After a time period controlled by 
the timer 151, the valve 16 is closed to halt the release of the gas prior 
to sufficient excess pressure being developed within the structure which 
can cause damage to the structure. After the release of gas has rapidly 
increased the pressure, the pressure then decays due to leakage so that at 
no time is a steady state reached or more specifically, the rate of feed 
of air is not controlled in order to obtain a steady state. 
If desired, an outdoor pressure transducer 21 may be operatively connected 
to the electronics package. 
Alternatively, a source of gas under pressure may be contained within a 
tank such as tank 10 and operatively connected to the interior of the 
house or building by means of a line or conduit 22 detachably connected to 
a valve 23 extending through a door 24 or the like, it being understood 
that the tank is situated externally of the building as shown 
schematically in FIG. 2. The electronics package 13, the valve controller 
17 and the fast acting valve 16 will, of course, be similar to those shown 
in FIG. 1. 
The apparatus of FIG. 2 is also modified by the addition of a pressure 
sensor 153 which is schematically illustrated and is attached to the 
vessel 10 and communicates the pressure sensed in the vessel to the 
electronics package 13. 
This arrangement can be used in a modified technique in which the pressure 
pulse is created as previously explained, with the sensor 152 responsive 
to the pressure in the interior of the building as indicated by a pressure 
gauge schematically indicated at 154. In this technique, however, the 
parameters required for the calculation of the air-tightness of the house 
are obtained firstly by a measurement of the pressure within the vessel 10 
immediately prior to the release of gas into the interior of the building 
and also the value of the peak pressure in the interior of the building as 
sensed by the sensor 154. From these two parameters the air-tightness of 
the building can be calculated. Calculation factors can be obtained 
empirically by simple tests using the specific apparatus concerned to 
calibrate the apparatus. 
The sensor 152 can either be arranged to sense specific points on the 
profile of the curve as previously explained, or can be arranged to 
develop an actual profile by sensing the varying pressure in the pulse as 
sensed by the detector 154. 
Since various modifications can be made in my invention as hereinabove 
described, and many apparently widely different embodiments of same made 
within the spirit and scope of the claims without departing from such 
spirit and scope, it is intended that all matter contained in the 
accompanying specification shall be interpreted as illustrative only and 
not in a limiting sense.