Commercial buildings which do not achieve Air Tightness often waste 20% to 40% of the total energy that they consume. When the building envelope is not tight energy is simply lost to the outside. Defective roof lights, smoke hatches and curtain walls, a result of poor design, defective construction, or incomplete maintenance is widespread. “We waste so much energy for no good reason” says SOLIDEA’s Steve Walker “Air Tightness is the big ticket cost in retail, commercial offices and hotels, and it has nothing to do with the level of Insulation installed”
What is Air-Tightness?
The level of Air Tightness in a building is measured as Air Permeability it is the measurement of the volume of air which leaks through the building envelope per hour per m² of building envelope at 50 Pascals Differential Pressure. Air Permeability is then expressed as a rate for example 3 m³/h. m² at 50 PA which is much better than 7 m³/h. m² at 50 PA. We can test Air Tightness on site and we can easily quantify the energy losses simply by measuring Air Permeability
How does Air Permeability differ from Ventilation?
Ventilation is the controlled Infiltration and Evacuation of Air whilst Air Permeability is the uncontrolled Infiltration and Evacuation of Air. The benefits of high Insulation levels and more energy efficient heating systems for example are lost if warm air can leak out of a building and cold air can leak in.
Does Air Tightness affect Ventilation and IAQ?
Very much so, Air Tightness in Commercial buildings is not just good practice its a must for any sustainable energy efficient installation. Without Air Tightness Ventilation systems “Slave” or demonstrate a phenomenon called “Racing” resulting in very high energy use and unusual extra over costs because they have to work much harder. Poor performance of Ventilation means very low IAQ. Sick Building Syndrome [SBS] occurs as a result of Air Permeability as do most unpleasant, unwanted smells and forced VOC’s often present in hotel guest rooms.
What is the impact of Air Permeability on Mechanical Air Handling?
Without Air Tightness, even the most simple Ventilation systems cannot perform efficiently, meanwhile the most advanced Ventilation systems demonstrate their worst energy performance and lowest IAQ as a result of Air Permeability. Frequent or regular pressure changes do not add value to the building environment by keeping mechanical handling systems busy. The cost of Air Permeability until air leakage is controlled is higher energy bills, more maintenance and shorter life cycle of plant and equipment.
How much can high Air Permeability cost my business?
A busy Retail Centre of 25,000m² Gross Internal Area [GIA]can easily achieve energy consumption levels below 180kW/m² per year if it has a low Air Permeability. That would mean 25% less consumption than many other Retail Centres in its class. With energy prices currently over 10 Euro Cents per kWh a 45kW/m² per year saving for 25,000m² GIA would represent a cost saving of at least 112,500 Euros per year.
A busy Office Centre of 10,000m² GIA can easily achieve energy consumption levels below 280kW/m2 per year if it has a low Air Permeability this would be more than 25% lower consumption than many other Office Centres in its class. With energy prices currently over 10 Euro Cents per kWh a 70kW/m² per year saving for 10,000m² GIA would represent a cost saving of at least 70,000 Euros per year.
How do you test a Commercial Building for Air Permeability?
It is possible to test most any size building for Air Permeability. The “Blower Door Test” system is quickly set up by experienced operatives and the whole process can often be completed in one day in normal weather conditions. Testing Air Permeability requires one or more fans blowing air into the building to reach an optimum pressure of 50 Pascals the testing equipment then measures the amount of air it needs to maintain that pressure. The resulting pressure loss data is provided to sophisticated calibrating software which accurately plots out loss. Thermography or Smoke is then used to find the leaks.
Before any meaningful test results can be achieved from the “Blower Door Test” building works must be completed tight and visual defects studies need to have been carried out to the satisfaction of an experienced facade and building fabric surveyors [see EVE® day time studies]. Visual defects studies are also very necessary before any Thermographic studies can be carried out [see EVE® night time studies] because it is very necessary to find and make good or at least understand common defects such as missing insulation, water egress and dissimilar building systems integration. Major facade defects will require the test be repeated many times and the results will not be sustainable unless the more obvious defects are first fixed the “Blower Door Test” is used at the end of defect rectification to find the remainder of the leaks and finally commission the building.
What are the main causes of Air Permeability?
Full life cycle, the weather plays the major roll, not just wind but thermal exposure or solar impact every system and every joint is expanding and contracting, every interface is subjected to continuous and relentless Dilatation in a commercial building.
Early in the buildings life cycle Dilatation may affect the performance of a facade increasing Air Permeability because of its Orientation and solar impact at different times of the day, and these defects remains undetectable to Thermographic studies [because you cannot use thermography in bright sunshine]. “Often a simple adjustment of joinery during the defects and warranty period can save a lot of trouble later on “Says SOLIDEA’s Steve Walker “but the builder is rarely called back after handover to take care of it”.
Too many interfaces and poorly designed weather proofing expedited by poor construction work, incorrect tolerances are all very good reasons why practically every building leaks. Although most system components come from a factory very Air Tight once incorrectly specified, installed or unfinished by building contractors they simply do not perform.
After being installed and interfaced with dissimilar systems most components need later adjustment and without this adequate maintenance Air Permeability failure is inevitable. Changes to the original building use design through tenant upgrades or using the fabric of a building as it was not intended often prove “big ticket” defects for the Air Tightness of a building.
Tenanted zones often suffer high Air Permeability because smoke stopping is inadequate around pipes and ducts, shop partitions are often incorrectly stopped and dampers and other necessary components in the mechanical air handling systems are defective. Shop units are effectively boxes within boxes and should test tight simply after stopping entrances.
When is the best time to test for Air Permeability?
SOLIDEA clients often require “Blower Door Tests” for commissioning and to close EVE® Stage ONE handover.”Blower Door Tests” can be required as part of final inspection of a building envelope performance for retail, office and many other environments. Logically this is after the initial schedule of defects is complete and has been handed over to the satisfaction of the Surveyor and the final handover is near. The EVE® Stage ONE handover program should be repeated every 5 years of the building life cycle or at least every change in ownership or handover the building and can be commissioned at the close of these milestones.
How accurate is Air Permeability testing?
Air Permeability testing can be completed with the help of Thermographic studies and when the temperature differential between inside and outside [or the other way round] is in excess of 10 degrees C. Meanwhile smoke generator tests can be completed at any time showing the route of the leak. Often the “Blower Door Tests“is reversed in some climates to create a negative pressure inside a building then Thermographic or smoke generator tests or even the back of the hand is deployed to locate leaks and even the very smallest of hot or cold leaks. Air Permeability is very accurate unlike other testing methods it not only confirms defects it quantifies it a big stress for a contractor.
Who needs Air Permeability testing?
Anyone who pays energy bills needs to monitor the use of energy. If energy is not monitored it is simply not managed. Commercial Centre owners, managers, operators and future buyers require whole centres to be tested it reduces risk it reduces costs.
More often tenant associations require building owners to test their buildings because each of the tenants share in the costs of energy consumed in circulation. Tenant associations like to monitor energy efficiency because to many it is a huge overhead
Tenants with many offices and shops need to monitor their consumption across the roll out and where side by side energy audit analysis requires, the single or group of least performing retail units need to be tested. Often low benchmarks can be deal breakers for retailers. The best Commercial Centre operators know their benchmarks well and make every effort to achieve lower benchmarks in future through their dedicated energy plan.
The fact is every tenant large or small needs be concerned with Air Permeability especially those wishing to monitor or negotiate its energy consumption. There is no limit to size of facilities to be tested large [including buildings 5 million m2] or small.
What does the building code require for Air Permeability?
Despite energy loss and the risk of cancer from Radon Gas [ the second largest risk for lung cancer after smoking] surprisingly very little.
There are no standards required and no test requirements as yet for the commissioning of buildings in Central Europe [“Blower Door Tests“are not a LEED requirement and nor is commissioning].
Blower Door Tests are required and strict stringent standards occur in advanced economies for example under LAT60 standards. Canada, Sweden and Norway are LAT60 societies where Air Permeability is simply not tolerated [for example most building types >1,3 m³/h. m²] a good guide is issued to testing standards elsewhere where Air Permeability is not tolerated including in Germany [for example >1,8 m³/h. m²]
Many European Countries are especially concerned as Radon Gas occurs in Air Permeable environments. The UK now requires [relaxed] standards and are very strict on testing [for example naturally ventilated building types <10 m³/h. m²] the standards will become more strict at each revision to 2020.
What standard of Air Permeability should we require now and in future?
As no strict regulations are yet enforced SOLIDEA Group have published a set of testing and design guide lines for building owners and designers in Central Europe based on its knowledge of already enforced LAT60 Standards and the new legislation and trends elsewhere in the European Union at the beginning of 2013. As 2020 draws nearer investors and tenants at least will require standards. Building owners and their representatives should feel free rather than compelled to better these rates
Does future Air Permeability standards affect building yields?
The tolerance of any building purchasers for energy inefficiencies are already history.
“Sustainable Building Investments”require benchmarking of any class of asset to ascertain the real energy consumption. Benchmarking and auditing is measured on the basis of real data not on assessors points and opinion. Energy is a cost and costs affect yields. This was not a risk for as long the tenant was willing to pay and the landlord was not to blame.
Commercial buildings are comprised of architectural systems and components manufactured and tested often of tolerances of <0,3 m³/h. m² Air Permeability and energy consumption is not at risk indicating and testing built environments at >3 m³/h. m² demonstrates more than a fair share of defect in design and construction.
An acceptable tightly designed and built building is easy to ventilate and a correctly ventilated building will for sure remain a yield asset with good building user opinion for many years to come because buildings don’t need to breathe only people do!