Top Fifteen Common Building Science Issues which affect your Home’s Performance

1. AC/heating system duct leakage
2. Insulation & thermal envelope failures
3. Incandescent lighting
4. Solar radiant heat penetration
5. Un-insulated or damaged AC/heating duct work
6. Missing air barrier
7. Improper AC/heating system air flow
8. Leaky building envelope
9. Pressure imbalances
10. Proper Air Filtration
11. Improper AC/heater/appliance/water heater maintenance
12. Combustible appliance flue or gas leakage
13. Proper fresh air ventilation
14. Outdated windows
15. Inefficient AC/heater equipment

1. AC/heating system duct leakage

Air conditioning and heating systems use forced air ducts to distribute conditioned air throughout the home.  According to Energy Star, in typical home, about 20% of the air that moves through the duct system is lost due to leaks, boot box connections, registers, air handlers, holes and poorly connected seams. 

The air handler, fan which blows the air through the air conditioning or heating system, creates significant positive and negative pressures which exaggerate the size of the actual leak.  A simple explanation of the impact of pressure on duct leakage is this.  “Does a balloon leak if it has a hole in it?  The answer is not what you expect.  A balloon only leaks if it has a hole in it and the balloon is blown up.  Your duct system acts like a blown up balloon when the system is running.

Supply side (exhaust) leaks cause a reduction in the amount of conditioned air to enter the living space effectively reducing the performance of the system.

Return side (intake) leaks cause hot (summer), dirty, polluted air to enter the system raising the ambient temperature of the air it is attempt to cool.  This causes the system to not achieve the temperature change in the air it is attempting to condition.  Return air leaks also cause polluted to not only clog key components of your mechanical system but degrade indoor air quality and cause dust in the home. 

2. Insulation & thermal envelope failures

Insulation is an important part of the energy system of your home.  Insulation works with other building components to maintain comfort while keeping the cost of heating and cooling down.  Insulation is a critical function in the prevention of heat transfer from conditioned and unconditioned space.  Without proper heat transfer management, a home’s performance will be dramatically impacted. 

When analyzing insulation, a homeowner must understand that there are two critical components:

1) Failure rate of the insulation;

2) Amount of insulation

Insulation must be properly installed to obtain its rating performance.  If a home has a failure caused from a compression, void or misalignment, the effective value can be dramatically reduced.  A 5% failure rate in insulation will cut its effective value in half.

In most climates, an attic should have a minimum of R-30 insulation but a performance home should aim for R-38.  Installing insulation above an R-38 value is not cost effective as the benefits begin to out weight the cost.                                                                                         

3. Incandescent lighting

Changing out all of your standard incandescent lighting to compact fluorescent lighting (CFL) is one of the fastest and easiest ways to save energy.  CFL’s uses 75% - 85% less electricity and last 8 to 10 times longer than incandescent bulbs.  Incandescent bulbs can also produce a significant amount of heat which causes the air conditioning systems to run significantly longer to cool the house.  The heat can also create uncomfortable conditions in the home.  An incandescent bulb when on will operate at 175 – 200 degrees Fahrenheit.

4. Solar radiant heat penetration

Windows on a typical home in the Phoenix area can account for nearly 50% of the workload placed on an air conditioning system. According to local utility companies, untreated windows allow about 20 times more heat into your home than an equal amount of insulated wall space.  By controlling the way the suns energy enters your home, you can save on summer energy bills.  Properly installed sunscreens will also improve interior fabric fading and improve a home’s comfort.

There are different options available to homeowners who have high solar heat gain common on east and west facing windows.   The best option is the seasonal installation of 80% or 90% shading coefficient sun shades.  Other options include 60% shading coefficient window coverings available from some suppliers. 

5. Un-insulated or damaged AC/heating duct work

Air conditioning and heating systems use forced air ducts to distribute conditioned air throughout the home.   When air conditioning ducts are not insulated properly, this causes the system to not achieve the temperature change in the air it is attempting to condition.  The air conditioning or heating system effectively cannot perform its job correctly and systems run longer, are more likely to breakdown and their life expectancy is shortened.

6. Missing air barrier

An air barrier is an air tight seal which eliminates connectivity between to spaces such as living space and the attic.  When open cavities such as columns, shoots, arches, architectural detail, mechanical shoots, drop sealing, etc. are not have a proper air barrier, air and heat can transfer from space to space.  Missing air barriers can be exaggerated by convection loops as heat rises and pressure imbalances throughout the home. 

Lack of air barriers also cause insulation to fail and minor failures in insulation have a dramatic effect on home performance. 

Simple stated, air barriers can be one of the most cost effective improvements a homeowner can make. 

7. Improper AC/heating system air flow

HVAC (Heating, Ventilation and Air Conditioning) systems are more than just a piece of equipment which heats or cool air.  A proper function HVAC system requires a proper air flow on both the intake (return) side and the exhaust (supply) side.  In Arizona, a number of new homes and HVAC retrofits have been constructed with improperly installed duct systems. 

To read more about efficient air conditioning and heating system function click on this link.  10 Components to an Efficient Heating & Air Conditioning System. 

8. Leaky building envelope

According to several energy studies performed over the years, air infiltration (air entering and leaving the building envelope) can consume a substantial amount of energy used for heating and cooling.  Drafty homes not only waste energy but make it almost impossible to maintain desired comfort levels.

Air leaks usually occur in the:

• Attic access
• Door sashes and frames
• Recessed lighting
• Electrical and plumbing penetrations
• Windows
• Chimney and fireplaces
• Drop ceilings

9. Pressure imbalances

Pressures caused by the air flow of the HVAC system, exterior conditions such as wind can cause pressure imbalanced in the home.  A pressure imbalance can create an environment as severe as a dangerous negative pressure to an uncomfortable room.  The common concerns with room pressure issues are:

• Negative pressure in a Combustible Appliance Zones (CAZ) to a high room pressures which will cause poisonous flue gas to enter a living area.
• High room pressures will cause bedrooms to lose conditioned air and prevent air from properly cycling back into the HVAC system for heating or cooling.
• Building Performance Institute standards recommend room pressures to be below 3.0 Pascal for proper efficiency and comfort.

10. Proper Air Filtration

Improper air filtration is a very common problem in many homes.  It is more than just changing the filters regularly all though that is very important.  Air filters and filter grills service more than one function.  Their job is not only to take the particulates out of the air but to do it while not restricting air flow.  This is not a simple task as the two work against each other in most case.  In order to accomplish these task affectively, a

properly sized grill and good quality filter need to be coupled and maintained.  Don’t be surprised if your home has an undersized return grill and your air conditioning or heating system is being starved for air.

You can perform a simple assessment of your home by reviewing the chart below and comparing it to your system.

			Grill Size**
Tonnage	CFM Rate	Duct Size	Bar- Faced*	Stamp Faced*
2	800	16"	400	480
2.5	1,000	18"	500	600
3	1,200	18"	600	720
3.5	1,400	20"	700	840
4	1,600	20"	800	960
5	2,000	22"	1,000	1,200
* Based on the ACCA Standards and Filter Manufactures Standards
** Square inches of grill space

11. Improper AC/heater/appliance/water heater maintenance

Home Performance is not just about making improvements to your home, proper home maintenance is just as critical.   When systems and mechanical equipment are not serviced and cleaned regularly, the energy efficiency, equipment life proper function of your home’s systems begin to deteriorate.  

HVAC System

A precision tune up on your HVAC system should occur before every heating and cooling season to insure cleaner, more efficient operation and help ensure future problems are discovered before they occur. Routine annual maintenance is vital to efficient, worry-free heating and cooling.  Common HVAC problems from lack of maintenance include dirty evaporator coils and clogged blower wheels.

Dryer vents

Dryer vents which are not properly maintained require dryers to use more electricity, exhaust pollutants into the air and cause over 15,000 fires each year.  Dryer vents should be cleans every 1-2 years depending on use.

Calcium Build Up

Washers, dishwashers and water heaters require regular maintenance to remove calcium build up.  Calcium and hard water are a leading cause of equipment failure and reduced manufacture efficiency

Refrigerators coils

A refrigerator functions just like an air conditioned and requires regular cleaning to maintain efficiency.

12. Combustible appliance flue or gas leakage

Combustible appliances produce toxic gases which can lead to severe illness and death.  Making sure appliances such as hot water heaters, furnaces and stoves are properly functioning and venting properly.  A properly trained building performance analyst will run test to verify that equipment if functioning properly and in an environment that insures safety. 

13. Proper fresh air ventilation

Indoor air quality is a critical component of your family’s health and wellness.  According to the Environmental Protection Agency (EPA), indoor air is 4 – 5 time more polluted than outdoor air and contaminate levels indoors can reach 25 times that of outdoor levels.  Managing the air exchange rate of your home is critical to a health environment.  There are a number of options available to homeowners to insure proper ventilation and air exchange rate.

High pollution areas such as bathrooms and kitchens should have direct ventilation through exhaust vans. 

14. Outdated windows

There are three major components to a window which impact how efficient the window is:

1. U-factor – effectively the insulation value of the window
2. Solar Heat Gain Coefficient (SHGC) – ability of a window to stop solar radiant heat gain
3. Air leakage – The amount of air infiltration associate with the window.

Typically, window replacement will improve all three efficiency factors of a window and ultimately improve the performance of a home.  Window replacement is usually an expense proposition and for client whose budget do not allow for replacement, REEIS recommends sealing the wind infiltration and adding sun screens to accomplish a similar efficiency effect. 

15. Inefficient AC/heater equipment

Since heating and cooling our homes accounts for the largest single component of our energy costs (over 50%), installing a highly efficient heating and air conditioning system is a good improvement which will reduce utility expenses and annual maintenance expenses.  Heating and cooling equipment are subject to efficiency ratings similar to mile per gallon comparisons in automobiles

A gas furnace has an “AFUE” (Annual Fuel Utilization Efficiency) rating which is a measure of the gas furnace’s efficiency in converting fuel to

energy – the higher the rating, the more efficient the unit.

A central air conditioning unit has a “SEER” (Seasonal Energy Efficiency Ratio) rating, which is a measure of cooling efficiency for air conditioners and heat pumps.  The higher the SEER, the more efficient the unit performs.  Older units typically have a SEER rating around 8 with newer units having a SEER rating as high as 21.  A 16 SEER unit will use 50% less electricity than an 8 SEER unit.

Inefficient appliances/water heater

High efficient water heaters and appliances can be an effective way to reduce energy bills.  Typically, REEIS does not recommend replacement of these products strictly for energy saving goals because according to Energy Star’s saving calculations, the cost of replacing such equipment can be significant in comparison to the savings.