"Heating a drafty house is like driving a car with the handbrake on".

Welcome to the information site for The Draft Detective and one of the easiest, cheapest, cleanest and greenest ways to improve the energy efficiency of your home. 

Draft proofing is one of the least expensive and most effective energy efficiency improvements in the home.

What is a Draft?

Technically "uncontrolled ventilation" drafts are the result of gaps, cracks and holes in the buildings structure, ie the walls, roof, floor, windows and doors. Temperature and therefore pressure differences between the inside and outside of a building cause warm air flowing out to be replaced by cold air flowing in; the opposite happens in hot climates.  On a windy day this effect will be amplified, but it happens whenever there is a temperature difference between the inside and outside.  

Many people assume the main drafts are from around windows and doors but this is often not the case. Drafts in most houses are the result of holes of all shapes and sizes, often in nooks and crannies throughout the house. To cut down on the amount of heat that escapes through these holes you want to know where they are, how big they are, and what you can do to make them smaller. 

The Draft Detective will help to find all the main drafts with ease.

The Cost of Drafts

If you were offered an investment where you put in £100, and were given back £75 every year that'd be an exceptional investment, yet it is the kind of return many householders could earn by carrying out some very basic draft sealing.

Energy prices are going up faster than incomes and there are many reasons to expect that this trend continue.  In the past 5 years we have seen an almost 75% rise in the price of gas and electricity and only a 20% rise in income.

Below is a graph of annual heat loss from a large, detached stone built property.  

A property like this one could half the heat lost through drafts with a thorough treatment of some filler, caulk and seals to the draft sources. By reducing drafts you capture the "low hanging fruit". 

Insulating walls and roofs, fitting new windows and doors, or installing solar panels or heat pumps will give a small fraction of the return on investment you can get through basic draft sealing. And you get paid back in three ways:

  1. Save money
  2. More comfortable home
  3. Lower carbon footprint

So Why have  We Ignored Drafts?

Up until around 30 years ago it was common to heat only one room in a house, usually with either a coal or electric fire. Everyone  learned to shut the door to that room. 

Nowadays with centrally heated houses we are less aware of  drafts, but they have not disappeared.

Brief History of the Blower Door

One response to the oil crisis of the 1970's in the USA was a determined bid to reduce energy waste in buildings.  Drafts along with lack of insulation are the main causes of energy waste in the home. The Blower Door (aka Draft Detective) was developed to find and measure the drafts.

Simple Yet Effective Tool

A blower door is basically a high powered fan which can be temporarily fitted into an external doorway. The fan is set to blow air out of the house which in turn causes an equal volume of replacement air to be sucked in. 

This simple yet effective process simulates a gale force wind blowing on all sides of the building at the same time. A calibrated pressure gauge measures the air flow and shows how relatively "leaky"  the house is compared to other properties (see footnote).

Blower doors have been used to improve energy efficiency in buildings in the USA, Canada and other European countries for decades. UK building standards recently began to require air leakage standards to be met in new housing. 

The Test

Witnessing the effect of the blower door can be a surprising and often enlightening experience. 

A variety of simple techniques can be used during a test to identify specific draft spots in individual rooms. Once you know where the main drafts are located, dealing with them is generally a cheap and straightforward DIY job involving basic sealants, fillers and draft strips. 

A test will normally take around an hour, and ideally a householder will be around to see the process. The test report will detail the extent of the drafts, including the main leakage areas and how best to seal them. 

More Information

To book a test or if you have any questions please call or email.

Andrew 07968 319833



Indoor Air Quality
Good Indoor Air Quality (IAQ) is vital for our health. It is affected by a variety of pollutants from the obvious ones such as dust, mould and tobacco smoke to the less obvious chemicals involved in the manufacture of many types of carpet and wood products. In addition combustion appliances, such as older boilers, open fires and other solid fuel stoves require a dedicated amount of fresh air supply to operate efficiently and safely. Condensation is another aspect of IAQ which can affect us and our home. It is due to a combination of too much moisture in the air landing on cold  surfaces with inadequate air exchange from that room to the outside or other parts of the house.  The vast majority of properties have far more drafts than benefits the health of either the occupants or the home. 

Building standards now require most new homes to be built to a standard air leakage rate of no more than 10 cubic metres of airflow an hour, per metre square of the properties surface area, at a test pressure of 50 pascals  (10m3/hr/m2 @50pa). Older stone built properties will often have a leakage rate of 12+m3/hr/m2. Good practice looks for a rate of 5 or less. It is not until below 3 that some form of mechanical heat recovery ventilation system is incorporated into the building to ensure adequate fresh air.