2. Draught Finder Trevor Clark 1. All About Air Qualified L1
Air Tester & Thermographer
Affiliate Member BINDT
(British Institute of Non Destructive Testing)
Independent Airtightness Testing Scheme
UK Thermography Association

3. Air – All About Air
This presentation is intended to provide a brief description of Air – and the problems Air gives buildings
What is Air?
Air consists of a number of gases and water vapour along with other particles of dust and other forms of pollution.
Air surrounds the planet and is called the atmosphere.
Air is fluid and will fill every available space. Due to the effect of the sun heating our atmosphere air is part of our weather system. Air flows from high to low pressure areas.
As it flows (as wind) the air pressure pushes against us and buildings, then 'pulls' air from within buildings as it passes.
Air being a mix of gasses and water vapour has, at different temperatures has varying capacity to hold heat energy for the same volume of air depending on the amount of moisture held in the air.
Warm air can hold a large amount of moisture, but as it gets colder it releases this moisture to condense back into water.

4. Air – All About Air WATER VAPOUR
Water vapour is picked up and carried by air.
The amount of water vapour in the air at any given time depends on the temperature of the air and is expressed in percentage terms as Relative Humidity.
Air at any temperature and 100%RH will not take up any more water vapour.
To increase the amount of water vapour in the air the temperature must be increased.
Lowering the temperature of the air results in the water vapour condensing out as water droplets.
The above statement is very important. Water damages building structures and leads to mould problems which in turn can cause serious respiratory health problems.
When constructing a property care must be taken to prevent water vapour passing from the warm (IN) side, to the cold (OUT) side of the structure. While we live in a mild climate water vapour condensing within the structure still does happen and the building should have an efficient VAPOUR BARRIER to prevent water vapour from a high pressure (inside) travelling to the lower vapour pressure (outside).
Building Air Tightness regulations also bring about the need for an AIR BARRIER and in general the structure should have a barrier that prevents both air and water vapour (moisture) from passing from inside to outside.

5. Air – All About Air BASIC PSYCHROMETRY
The air that surrounds us behaves in a "known way" and according to the laws of physics we can use mathematics to predict how air at one particular point will behave as the temperature and pressures around it change.
We can predict how much energy the air has at this starting point and how much energy this known volume of air will require to increase its temperature, how this will affect the volume and its ability to hold water vapour.
We can also predict how much energy will be needed to be removed to reduce the temperature and how this will affect the ability to hold water vapour.
We can also predict when the air will become saturated, at what temperature and how much water will be removed if we continue to cool the volume of air.
All we need is a chart that allows us to quickly establish where the starting point is for this volume of air and two measurements.
A Dry bulb temperature and
A Wet bulb temperature
These readings are taken from a "Sling Psychrometer".

6. Air – All About Air
BASIC PSYCHROMETRY

7. Air – All About Air BASIC PSYCHROMETRIC CHART
Using a Psychrometric Chart we plot this starting point on the chart, in this instance the dry bulb was 21°C with wet bulb showing 14.8°C.
If you follow the blue dotted line, it shows a figure of 50%RH (Relative Humidity). This is our starting point.

8. Air – All About Air BASIC PSYCHROMETRIC CHART
If we now heat the air to 30°C our measurement point moves horizontally to the right, while the wet bulb temperature also increases to 17.5°C and the RH has dropped to 29%.
Nothing else has changed just the temperature because we have added heat energy to the air.

9. Air – All About Air BASIC PSYCHROMETRIC CHART
If we now cool the air back to our starting point and continue to cool down to 5°C our measurement point moves horizontally to the left, while the wet bulb temperature also decreases to 5°C.
When we reach 10.4°C what has happened, where has this water come from?
While the RH has changed to 100%. Nothing else has changed just the temperature because we have removed heat energy from the air.
Yet water has appeared from "nowhere" !
Note: The 100%RH line has changed to a solid line, this is called the "Dew Point" where air containing water vapour cools to the point where it can no longer hold the vapour and it condenses out of the air, leaving water behind.

10. Air – All About Air DEW POINT & CONDENSATION
From the chart we can predict the weight of water that will be condensed out of the air when cooled below the Dew Point.
Air always contains water vapour to some extent, but is capable of holding high quantities of water vapour when heated.
During the winter we have warm moist air within the building, which is naturally going to try to get to the lower temperature and lower water vapour pressure outside the building.
ANY hole, crack or fissure in the building is going to allow air to escape (or enter) uncontrolled and carry with it this moist warm air.
As we have seen from the above example as the air is cooled as it travels to the colder outside air there comes a point when the water vapour cannot remain a vapour and condenses.
If this is outside the insulation then all would be OK, but this seldom happens!

11. Air – All About Air DEW POINT & CONDENSATION INTERSTATIAL CONDENSATION
Overtime this condensed water will lead to;
1. Major reduction in the performance efficiency of the insulation.
2. Increased heating costs.
3. Potential mould growth within the structure.
4. Mould growth on the inside of building.
5. Smells from the building due to the rotting process
6. Rotting of the structure.
7. Possible failure of structure.
This physical property of air and water vapour is extremely BAD for buildings, especially if it should happen within the insulated part of the structure.
We need to stop this from happening,
But How ?

12. Air – All About Air BARRIERS – AIR & VAPOUR
We need to install a BARRIER that will prevent air from leaving the building by any pathway it can find.
Holes, Gaps, Cracks of Fissures in the building envelope will allow air to enter or leave.
By preventing the air from flowing through the structure we prevent the water vapour from being carried with the air and condensing.
But, we must also control the air that enters or leaves the building to maintain good comfortable conditions within the building. (a Ventilation System) 
Today's modern buildings have two barriers installed on the warm side of the insulation to control this air movement and the barriers used generally perform a twofold function;
Vapour Barrier - stops water vapour
Air Barrier - prevents air infiltration or exfiltration.
Most new buildings now also incorporate a WIND Barrier which is installed on the outer cold side of the insulation reduce or prevent wind from blowing into the building.

13. So, how much water vapour can pass through a structure in 24 hours?
Air – All About Air
BARRIERS – AIR & VAPOUR
With increased insulation standards in modern buildings the average internal temperature has risen over the last 10 years by 3.50C.
This temperature rise means that air in the conditioned space can hold more moisture than ever before.
In this way the air/vapour barrier has a critical role.
A leak in the Barrier becomes very important, not only from an energy perspective, but also from a moisture management perspective.
So, how much water vapour can pass through a structure in 24 hours?
A German building research establishment found that for a typical timber frame wall section one meter by one meter with a good quality vapour/air barrier would let 0.5 grams of water vapour through in 24 hours when the inside temperature was 20°C and outside was at 0°C.

14. Air – All About Air BARRIERS – AIR & VAPOUR
1 square meter of typical wall with conditions as indicated.
0.5 grams of water vapour pass through in 24 hours.
1 square meter of typical wall with identical conditions.
But with a gap of 1mm, a typical joint in plasterboard sheeting.
In 24 hours …
800 grams of water vapour passed through this small gap!
That’s about a pint and 2/3rds
Barriers should be continuous and intact … or else!

15. Air – All About Air BARRIERS – AIR & VAPOUR
However the Air Barrier (with vapour control layer) will prevent air carrying moist air from getting through to the insulation layers and therefore stops water vapour from condensing within the insulation. The use of an AIR/VAPOUR BARRIER also;
Lowers ENERGY RUNNING COSTS, less energy input
Improves COMFORT CONDITIONS, steady temperatures
Improves INDOOR AIR QUALITY, providing sufficient ventilation is installed
Quicker HEAT UP TIME, retaining heat longer.
Less DIRT & GRIME, brought into the building, Reduced Washing cycles
Improves INSULATION PERFORMANCE, prevents air blowing through or around insulation
Improves ACOUSTIC PERFORMANCE, less noise transmitted
Improves OCUPANCY SATISFACTION, fewer complaints from tenants, reduced rent disputes
Avoidance of moisture related BUILDING DAMAGE, lower maintenance
Lower ENERGY CAPITAL EQUIPMENT COSTS, smaller replacements required
Improved BUILDING STANDARDS, Builders take more care when building
Less CO² used in heating or cooling – Helping Government meet CO² reduction targets

16. Find the Draughts – Seal Them & Start saving PERMENANTLY
Air – All About Air
BARRIERS – WIND, AIR & VAPOUR
However the biggest & best reason for having an Air Barrier is that it WILL
SAVE YOU Money on
Heating Energy Costs
Find the Draughts – Seal Them & Start saving PERMENANTLY

17. “AIR & VAPOUR BARRIERS”
Air – All About Air
If you are experiencing any of the problems in the previous slides, please call TREVOR for an informal discussion on how we can help reduce your heating costs Mob:
Trevor Clark
Qualified Air Tester & Thermographer
Thank you for reading …. Check out our other Slide Presentations in this series
“AIR & VAPOUR BARRIERS”