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Advanced Building Systems
Heating Systems
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Heating Systems
 
In this course, you will learn about:
 
1. Legal requirements pertaining to heat and hot water.
 
2. The physical characteristics of heat.
 
3. The two main kinds of central heating systems and the principles behind each.
 
4. The gravity and motor driven fan systems in warm air systems.
 
5. The hot water system: open and closed.
 
6. The Steam System
 
7. How to maintain each kind of system.
 
8. Fuel oils
 
View Sample Pages of a residential Oil Burner
 
9. Controls on the #6 burners
 
10. Your role in the prevention of air pollution. 

steamsystem1.jpg

After completion of this course, you will be able to:
 
1. List the basic requirements discussed in the NYC Housing Code.
 
2. Indentify and describe the 3 characteristics of heat.
 
3. Explain the principles behind the two main kinds of heating systems.
 
4. Explain how the gravity and motor-driven fan systems work.
 
5. Describe the open and closed systems.
 
6. Describe how the steam system works.
 
7. Describe how to maintain each kind of system.
 
8. Describe the different kind of fuel oils.
 
9. Explain the purpose of th controls on the #6 burners.
 
10. Describe the procedures you must follow to prevent air pollution.

Heating Systems
 

A)  Different Types of Fuel to Heat your Building

  1. Coal
  2. Wood
  3. Solar
  4. Oil (most common - 3 types = #2, #4 and #6)
  5. Gas

British Thermal Unit - BTU

An international uni of measuring heat.  How much heat it takes to raise raise the temperature of one pound of water one degree fahrenheit.

B.  Types of Heating Systems

  1. Steam System - is a central heating system that produces steam (212 degrees).  Water is heated to produce steam which is carried through the system to radiators in each apartment.  More expensive - Gives more BTU's but uses more fuel.

   Pipe steam system is the most common type of system

   2.  Hot Water Systems - sends hot water through sytem via a pump
        forces the heated water through the system to the radiators
        in each apartment.  Some systems use copper tubing that
        carries the water and is feed through the baseboard heating.
        This is cheaper, more efficient and uses less BTU's and can
        easily be regulated.

    3.  Forced Hot Air Systems - boiler heats air that is forced througH
         the system with fans that carry the heated air thru ducts
         and baseboard heating.  Dry system that is not very efficient.

The Landlord must provide hot water at the tap at 120 degrees fahrenheit.  The heating season is from October 1 - May 31st.  Landlord must provide heat during the time if:

Time of day

6AM - 10PM  outside temp is 55 or below and the inside temp is 68

10PM - 6AM outside temp is 40 or below and the inside temp is 55

One Pipe Steam System - Most common type - has a boiler that is fueled by oil or gas and heats water to boil to produce steam.  This steam is carried through the system through pipes called Risers that are connected to radiators in each apartment.

On and Off Valve - opens and closes radiator to allow steam in.  Should be either all the way opened or closed and NOT PARTIALLY OPENED.

Air Vent - Allows air out of the radiator so that steam can fill it.  Closes once radiator is filled with steam trapping it inside.

Radiator - should be pitched (tilted) toward the ON/OFF VALVE so that condensate (steam that has cooled and turned back into water) can flow back to the boiler.  If not, you will hear banging and the radiator will not heat properly.  Also the Air Vent should be open and working so that air can be displaced by steam or else the radiator will not heat up.

Boiler Safety Controls:

Three basic Safety Control Items to focus on:

  1. Carbon Monoxide - poisonous gas
  2. Steam Pressure - measured by gauge - can explode
  3. Low water - no water in boiler will crack boiler

PRESSURE SAFETY CONTROLS

1.  Boiler Pressure Guage - measures pounds of pressure per square inich (0-13) where a measurement of 15 psi will blow up a boiler.  3 - 4 PSI is a safe operating range for the boiler.  This guage also allows you to see how much pressure is building up in the boiler.

2.  Pressuretrol and the Manual Reset Pressuretrol - can be set automatically set off boiler when pressure rises to a certain level.  This can also be done manually where you have to physically go and reset your boiler.

3.  Safety Pop Up Value - Allows steam to pop off to release pressure when the other back up does not work.  Set at 12 PSI.

LOW WATER SAFETY CONTROLS

1.  Glass Gauge - shows you amount of water in boiler - should be at a certain level.

2.  Low Water Cut Off - floats on the level of the water if the AUTOMATIC WATER FEED is attached to low water cut off - will refill boiler when water gets too low.  NOt a good idea for 2 reasons - ONE: wasted water indicates a leak - losing water somewhere in the ssytem.  It costs more to refill.  TWO: Wastes energy - cold water is refilled into boiler takes more energy to reheat this new water.

Your boiler should be a closed system which recycles the same water over and over again.

Heat Timer

Has an outside thermometer or sensor that measures the outside temperature and will turn the boiler based on the code requirements of outside/inside temperature, the time of day, etc.  Has controls to regulate the amount of heat sent up to apartments and lets you know when the building is totally heated.


Fuels

  1. No. 2 Oil - a light refined oil used for smaller buildings (about 20 units)
  2. No. 4 Oil - a heavier oil that is a mix of #2 and #4 used in middle sized buildinigs
  3. No. 6 Oil - a heavy thick residual oil that is cheap and produces the most BTU's.  Needs to be preheated due to its tar-like constituency and the super needs to be licensed in order to handle it.


 

GENERAL DAILY BOILER MAINTENANCE REQUIREMENTS

DESCRIPTION

COMMENT

Check temperature of exhaust gases at two different firings.

Compare temperatures with tests performed after annual cleaning.

Check Steam Pressure or Water Pressure/Temperature

Is Variation in steam pressure or water pressure/temperature under different loads? Wet steam may be produced if the pressure drops too fast (caused by excessive loading on the boiler).

Check for Unstable Water Level

Common causes of unstable water level are:

  1. Contaminates in boiler such as oil, excessive solids, excessive feedwater treatment, etc.
  2. Overload on boiler
  3. Malfunctions in equipment such as feedwater pump, water level control, etc.

Check Burner

  1. Are controls functioning properly?
  2. Is Burner clean? The burner may need cleaning several times daily if no. 6 fuel is used.

Check Motors and Auxiliary Equipment

Check to see that motors and auxiliary equipment are functioning properly.

Check Air Temperature In Boiler Room

The air temperature in the boiler room should not exceed or drop below recommended limits. These limits are determined by measuring the composition of the exhaust gases.

Check Blowdown

  1. Manual Blowdown -- The frequency and amount of blowdown will depend upon the amount and condition of the feedwater. Check to see that the blowdown valve does not leak.
  2. Automatic Blowdown -- Check operation of system and make sure that excessive blowdown does not occur.

Records

Keep daily records on:

  1. Type and amount of fuel used
  2. Exhaust gas temperature and position of firing
  3. Boiler room temperature at time (b) is measured

GENERAL WEEKLY BOILER MAINTENANCE REQUIREMENTS

DESCRIPTION

COMMENT

Check Exhaust Gas Composition and Temperature

  1. Measure exhaust gas composition and temperature at selected firing positions
  2. Recommended percentages of oxygen and carbon dioxide in exhaust gases are:

FUEL O2 (%) CO2 (%)

Natural Gas 1-1/2 10

No. 2 Fuel Oil 2 11-1/2

No. 6 Fuel Oil 2-1/2 12-1/2

Coal 3-1/2 13-1/2

These percentages may vary due to variations in composition of fuel.

Check Relief Valve

  1. Open valve manually while boiler is operating and observe steam pressure and force required (sometimes used).
  2. Check to see if relief valve leaks.

Check Water Level Control

Stop feedwater pump and allow control to stop fuel flow to burner. Do not allow water level in boiler to drop below the recommended low level.

Check Pilot and Burner Assemblies

  1. Clean Pilot and burner assemblies following recommended procedures.
  2. Check Assemblies:
  1. Spark gap
  2. Condition of electrode
  3. Condition of burner

Check Boiler Operating Characteristics

  1. Stop fuel flow to burner and observe flame failure (characteristics and timing)
  2. Start boiler and observe characteristics of flame

 

GENERAL MONTHLY BOILER MAINTENANCE REQUIREMENTS

DESCRIPTION

COMMENT

Check Exhaust Gas Composition and Temperature

  1. Measure exhaust gas composition and temperature at selected firing positions
  2. Recommended percentages of oxygen and carbon dioxide in exhaust gases are:

FUEL O2 (%) CO2 (%)

Natural Gas 1-1/2 10

No. 2 Fuel Oil 2 11-1/2

No. 6 Fuel Oil 2-1/2 12-1/2

Coal 3-1/2 13-1/2

These percentages may vary due to variations in composition of fuel.

Check Blowdown and Water Treatment Procedures

  1. Determine if blowdown procedure is adequate to prevent buildup of solids in boiler
  2. Determine if water treatment procedure is adequate to prevent undesirable effects

Exhaust Gases

  1. Measure exhaust gas composition and temperature over entire firing range
  2. Compare composition and temperature readings with those of previous months and reference data

Combustion Air Supply

  1. Check combustion air inlet to boiler room to be sure adequate openings exist
  2. Check combustion air inlet to boiler, and clean if fouled

Check Fuel System

Check pressure gauge, pumps, filters, and transfer lines. Clean filters as required.

Check Belts and Packing Glands

  1. Check belts for damage and proper tension
  2. Check packing glands for proper compression and leakage

Check for Air Leaks

  1. Around access openings
  2. Around flame scanner assembly

 

GENERAL ANNUAL BOILER MAINTENANCE REQUIREMENTS

DESCRIPTION

COMMENT

Check Exhaust Gas Composition and Temperature

  1. Measure exhaust gas composition and temperature at selected firing positions
  2. Recommended percentages of oxygen and carbon dioxide in exhaust gases are:

FUEL O2 (%) CO2 (%)

Natural Gas 1-1/2 10

No. 2 Fuel Oil 2 11-1/2

No. 6 Fuel Oil 2-1/2 12-1/2

Coal 3-1/2 13-1/2

These percentages may vary due to variations in composition of fuel.

Clean Waterside Surfaces

Follow manufacturer's recommended procedure in cleaning and preparing waterside surfaces

Clean Fireside

Follow manufacturer's recommended procedure in cleaning and preparing fireside surfaces

Repair Refractories on Fireside

Use recommended materials and procedure to repair refractory

Relief Valve

Remove and recondition or replace

Feedwater System

  1. Clean condensate receivers, and deaeration system
  2. Clean and recondition feedwater pumps

Fuel System

Clean and recondition system pumps, filters, burner, pilot, oil preheaters, oil storage tanks, etc.

Electrical Systems

  1. Clean all electrical terminals
  2. Check electronic controls and replace any defected parts
  3. Check mercury switches and replace if deterioration has occurred

Hydraulic and Pneumatic Valves

Check operation and repair any leaks

Start-up and Operation

Follow start-up and operation procedures

Exhaust Gases

  1. Make adjustments to give desired exhaust gas composition
  2. Record composition, firing position and temperature

 

Heating Systems - Heating systems, boilers, piping, heat capacities ....
A Guide to Convective Air Flow from Heat Sources
A table that can be used as a guide to convective air flows from heated sources. .
Building Elements - Heat Loss and Thermal Resistivity
Thermal resistance in common building elements as walls, floors and roofs above and below the ground .
Calculating Flow Rate in a Heating System
Basic equations for flow rate calculations in heating systems. .
Chimney And Fireplace Sizing
Chimney and fireplace sizing related to fireplaces and stoves that burns wood or coal as fuel. .
Circulating Pressures for Gravity Heating Systems
The circulating pressure due to the gravity difference between hot and cold water in self circulating heating systems. .
Classification of Coal
Based on volatile matter and cooking power of clean material. .

  • Classification of Oil - Classification of oil based on BS 2869 .
  • Classifications of Heating Systems - Classification of Hot Water Heating Systems by pressure or piping system. .
  • Design Procedure for Heating Systems - .
  • Food and Foodstuff - Specific Heat Capacities - Specific heat capacity of some common food and foodstuff as apples, bass, beef, pork and much more .
  • Heat Carrying Capacity of Copper Tubes - Hot water heat carrying capacity of copper tubes type L. .
  • Heat Emission from Pipes Submerged in Oil or Fat  - A table with heat emission from steam or water heating pipes submerged in oil or fat. The heat transmission is indicated for assisted (forced) and natural circulation. .
  • Heat Emission from Pipes Submerged in Water - Heat transmission from steam or water heating pipes submerged in water. Heat transfer rate for assisted (forced) and natural circulation. .
  • Heat Emission from Radiators and Heating Panels - The heat emission from radiators and heating panels depends on the inlet, outlet and surrounding temperatures. With this formula the heat emission at different circumstances can be calculated. .
  • Heat Loss from Oil Filled Tanks - A table with heat loss from heated oil tanks. .
  • Heat Loss from Oil filled Tanks and Pipe Lines - Estimate the heat loss from oil tanks and oil pipe lines with this table. .
  • Heat Loss from Open Water Tanks - Due to evaporation the heat loss from open water tanks can be considerable. This table indicate the evaporation, radiation and heat transfer loss from an open tank. .
  • Download the ASHRAE Standards - ASHRAE has over 175 standards, some written jointly with ANSI and IES. ASHRAE standards describe uniform methods of testing, specify design requirements, and recommend standard practices. They also publish numerous handbooks on fundamentals, applications, refrigeration, and several other comprehensive subjects.
  • Heat Losses from a Building - Calculating the heat loss from a building. .
  • Hot Water Heating Systems Design - An introduction to Gravity Heating Systems and Forced Heating Systems. .
  • Indoor Design Conditions for Industrial Product and Production Processes - Recommended indoor temperature and humidity for common industrial product and production processes. .
  • Recommended Flow Temperatures in Heating Systems - .
  • Resistance of Fittings in Pipe Heating Systems - .
  • Resistance of Fittings in Terms of Equivalent Length of Straight Pipe in Heating Systems - Resistance table to calculate fitting head loss in meter or feet in heating systems. .
  • Safety Valve Standards - An survey of international safety valve standards. The most common used standards in Germany, UK, USA, France, Japan, Australia and Europe. .
  • Safety Valves and Relieving Capacity - Maximum safety valves free air relieving capacity .
  • Safety Valves in Heating Systems - Sizing of Safety Valves for boilers 275 to 1500 kW. .
  • Static Pressure in a HVAC System - The static pressure in a HVAC system is the system pressure that avoids drying out the tops of the system. .
  • Temperatures for Indoor Design - Recommended indoor temperatures summer and winter.


  • The Overall Heat Transfer Coefficient for Different Fluids and Surfaces - A table with average overall heat transmission coefficients for different fluids and surface combinations - Water to Air, Water to Water, Air to Air, Steam to Water and more. .
  • Unit of Heat - Unit of heat - Btu, Calorie and Joule. .
  • US Design Outdoor Temperatures and Relative Humidity's in Winter and Summer - Outdoor temperatures and relative humidity's in different US states and cities summer and winter. .
  • What is Heat, Work and Energy? - A brief explanation and tutorial about the heat, work and energy. Including essentials as specific heat and specific heat capacity. .
  • Wood and Combustion Heat Values  - Combustion heat values for Pine, Elm, Hickory and many more species .

    Heat Losses from a Building

    Calculating the heat loss from a building.




    Heat loss from a building can be calculated as

    H = Ht + Hv + Hi



    1. Heat loss through walls, windows, doors, ceilings, floors, etc.

    Roofs should be added 15% because of radiation to the space
    H = 1,15 AU(ti-to)

    Walls and floors against earth
    H = AU(ti-te)
    where te is earth temperature


    Ht = AU(ti-to)

    where

    Ht = heat loss transmittion (W)
    A = area of exposed surface (m2)
    U = overall coefficient of heat transmission (W/m2K)
    ti = inside airtemperature (oC)
    to= outside airtemperature (oC)


    Coefficient of heat transmission U can be calculated as

    U = 1/(1/fi + x1/k1 + x2/k2+ x3/k3+..+ 1/fo)

    where

    fi = surface conductance for innside wall (W/m2K)
    x = thickness of material (m)
    k = thermal conductivity material (W/mK)
    fo= surface conductance for outside wall (W/m2K)



    C = k/x = conductance = heat flow through unit area in unit time (W/m2K)



    R = x/k = 1/C = thermal resistivity (m2K/W)

    Walls and floors against earth
    1/U = Re +
    SR


    1/U = Ri + R1 +R2 +R3 +..+ Ro



    2. Heat loss by ventilation

    Heat loss by forced ventilation

    Hv = cprqv(ti-to)

    where

    Hv = heat loss ventilation (W)
    cp = specific heat capacity of air (J/kg/K)
    r = density of air (kg/m3)
    qv = volume flow ( m3/s)
    ti = inside airtemperature (oC)
    to = outside airtemperature (oC)




    3. Heat loss by infiltration

    Heat loss by infiltration or "natural" ventilation

    Hi = cprnV(ti-to)

    where

    Hi = heat loss infiltration (W)
    cp = specific heat capacity of air (J/kg/K)
    r = density of air (kg/m3)
    n = number of airchanges (1/s)
    V = volume of room (m3)
    ti = inside airtemperature (oC)
    to = outside airtemperature (oC)

    This can be used together with Termal Resistivity.


  • Heating, Ventilation & AC Basics

    The purpose of heating, ventilation and air-conditioning systems (HVAC) is to heat, cool, control humidity and ventilate (introduce fresh air into) the building. Employee and customer comfort is the first priority of HVAC systems. HVAC systems are among the largest energy end-uses in commercial buildings throughout this region.

    There are many types of heating, cooling, and ventilation systems. Heating systems include boilers, furnaces, electric resistance elements and heat pumps. Cooling systems include window air conditioners, packaged (Direct Expansion or DX) units, heat pumps, chilled water systems and evaporative coolers. Ventilation and air distribution may be directly from the HVAC fan into the space, or through a network of ducts and/or air plenums. HVAC systems can be quite complex both in equipment and controls, and changes in one part of the system will have impact on other elements.

    HVAC and Energy Use
    HVAC systems can waste energy in four basic ways:

    Thermal Losses . Heated or cooled air will lose some of its thermal property through convection or conduction as it travels through the ducts of the air distribution plenums.

    Improper Sizing . HVAC systems are often oversized to ensure that sufficient air conditioning is always available, but this can also lead to significant operating inefficiencies.

    Excessive Demand . Increased HVAC load due to an inefficient building envelope or waste heat generated by lighting and equipment can cause the HVAC system to operate at higher levels for longer periods of time than is necessary.

    Poor Control Strategies . Temperature settings, hours of operation, seasonal conversions and other methods of control are frequently not given adequate consideration or implementation.

    Inefficient Equipment . Often older HVAC equipment and inexpensive equipment is not as efficient as other available HVAC technologies.

    Reducing HVAC Energy Use
    There are four simple guidelines to reducing HVAC energy use:

    1. Reduce operating hours by turning systems off when they're not needed.

    2. Improve operating efficiency of the systems by adjusting temperature settings and performing regular cleaning and maintenance.

    3. Replace existing components or systems with more efficient equipment.

    4. Increase system efficiency by installing improved controls and advanced control strategies.

    No-Cost Opportunities

    Manual Control
    HVAC operating hours can be reduced in many commercial buildings by simply turning off HVAC systems when they are not needed, for example, when the building or zone will be unoccupied for an extended period. Operable windows and fans provide air movement and natural "free" cooling on moderate days, which are prevalent through much of the year in this area. Ventilating with mild outside air is much less expensive than mechanically cooling the building air, which is warmed by people, lights and equipment.

    Adjust Temperature Settings
    Lowering thermostat settings just a few degrees during the heating season and raising thermostat settings during the cooling season is an easy and effective method of saving HVAC energy. In this region, reducing the heating temperature by an average of just 3 degrees throughout the heating season will reduce heating energy usage by about 13%. Energy savings are even greater, per degree, for raising air conditioner thermostat settings than for reducing heating levels.

    Some experimentation will be necessary to find the optimal settings that maintain comfortable conditions for employees and customers. Allowing and encouraging employees to dress comfortably and seasonably will make it easier to adjust thermostat settings without creating discomfort.

    Low-Cost Opportunities

    Building Envelope and Lighting Improvements
    Improvements in the thermal properties of the building envelope and in the efficiency of the lighting systems will reduce the load on the HVAC system. Any improvement to the building that reduces summer heat gain and/or winter heat loss will result in HVAC energy cost savings.

    Furnace and Boiler Maintenance
    Periodically perform combustion efficiency testing and combustion rate adjustment for gas-fired heating equipment. Replacing air filters and cleaning intake screens will also help gas-fired equipment operate more efficiently. Good maintenance practices can reduce fuel costs by 5-10%.

    Cooling System Maintenance and Cleaning
    Air conditioners, heat pumps, chillers and cooling towers all work by thermal transfer, moving heat from one place to another. Heat transfer surfaces, such as cooling coils, condenser coils, heat exchangers and evaporator surfaces, should be clear of dirt, grease and other obstructions. Select a technician to regularly inspect, treat and maintain the major cooling equipment in your building.

    Ductwork Maintenance
    Air duct joints and elbows should be appropriately sealed. Damaged or disconnected duct sections should be repaired and air filters should be regularly replaced. Ductwork in unconditioned spaces, such as on roofs and in attics, should be insulated. Energy is often wasted in commercial buildings due to leaks and poor insulation in HVAC ductwork.

    System Balancing
    Select an HVAC technician to periodically balance the HVAC air and water distribution systems. This maintenance procedure will help maintain appropriate and efficient space temperature control throughout the building.

    Install Programmable Thermostats
    Programmable thermostats are simple microprocessor-based units that accurately maintain system start-up and set-back schedules, and eliminate unnecessary HVAC use during hours when the building is normally not occupied. Improved controls are a small investment that may yield large improvements in HVAC energy efficiency.

    Building Envelope Basics

    The building envelope is comprised of the foundation, floors, walls, roof, windows, exterior doors and other components separating the "inside" from the "outside" of a building. This "shell" is an integral part of the energy system. The ability of the foundation, walls and roof to isolate occupants from outdoor conditions significantly impacts the operation of HVAC systems. Windows, doors, skylights and other apertures impact interior lighting and ventilation conditions in addition to heating and cooling demands.

    The building envelope, lighting, and HVAC systems should work together to optimize energy efficiency and provide a comfortable, pleasant environment for employees and customers. For example, high efficiency lighting reduces air conditioning costs since less heat is generated in the building by the high efficiency lighting.

    If the building envelope is "tight," the outside temperature fluctuations will have less impact on the building HVAC systems which work to maintain indoor temperatures. In Southern California, however, buildings can also take advantage of typically mild ambient conditions. In fact, for many commercial buildings the HVAC systems primarily work to remove interior heat (from occupants, lighting, and equipment) from the building. For these buildings, a well-insulated "tight" envelope will actually increase HVAC energy consumption.

    Building Envelope and Energy Use
    The building envelope can waste energy in four basic ways:

    Air Leakage . Conditioned (heated or cooled) air leaking out of the building, or outside air leaking in, through surface cracks and openings around windows and doors can dramatically increase the amount of energy needed to operate HVAC systems in order to maintain building comfort.

    Poor Insulation . Heat transfer into the building in summer, and out of the building in winter, through window glass or poorly insulated walls, ceilings and doors can also increase the amount of energy needed to operate HVAC systems.

    Ventilation and Humidity . The building envelope plays an important role in the ventilation of the building, that is the movement of air and moisture in and out of the building. The envelope should be designed in conjunction with the ventilation system to prevent excess condensation on windows and walls that can cause mildew and rot problems.

    Excess or Insufficient Sunlight . Good envelope design can allow the sun's light and heat in when desired, and deflect them when unwanted. The building envelope influences the artificial lighting systems and HVAC equipment sizing needed to maintain comfort in the building.


    Reducing Energy Use
    There are several inexpensive ways to reduce energy usage due to building envelope problems. The ideas detailed below fall into the general strategies of:

    1. Reducing air infiltration.

    2. Reducing heat transmission.

    3. Controlling humidity.

    4. Controlling sunlight.

    No-Cost Opportunities

    Isolate Unused Areas
    Closing HVAC dampers and sealing exterior windows can isolate spaces that are not occupied by people and may not need space conditioning. Isolating unused areas of the building results in a reduction of the total conditioned space and the energy used by the HVAC system.

    Door and Window Frames
    Tightening window and door frames will ensure that they are closely attached to the building and minimize unwanted air leaks. Automatic door closers should be periodically adjusted to ensure that they close the door completely and rapidly.

    Low-Cost Opportunities

    Seal Cracks
    Cracks may occur in foundations, walls, roofs and around apertures (windows, doors, and skylights) as well as flue chases, pipes and conduits leading into the building. Normal use, thermal expansion and contraction, material aging, foundation settling, or seismic damage can cause these cracks. Sealant caulking will eventually dry out and separate from building material surfaces. A variety of glass fiber, expanding foam, silicone and acrylic products can be used to repair cracks or restore damaged seals in the building envelope.

    Install Air Conditioner Covers
    Placing exterior insulating covers on window-mounted air conditioners during winter months will prevent air leakage both through and around the unit.

    Install Weather-stripping
    Installing rubber blade or brush-type door sweeps on the bottoms of exterior doors, or rubber weather-strips on thresholds, will limit airflow beneath the door. Rubber strips can also be used between double doors. Weather-stripping can be added around doorframes with metal or plastic "V" strips or adhesive-backed foam strips. Operable windows, particularly double-hung windows, may also benefit from the installation of thin foam weather-stripping.

    Window Repairs
    Broken or cracked windows should be repaired as soon as possible. Heavy gauge transparent tape can be used as an interim measure.

    Shading Devices
    Installing interior operable shading devices (blinds and shades) gives building occupants the ability to deflect direct sunlight when it is undesirable. This will reduce unwanted glare and temperature buildup in the building.

    Building Envelope Basics

    The building envelope is comprised of the foundation, floors, walls, roof, windows, exterior doors and other components separating the "inside" from the "outside" of a building. This "shell" is an integral part of the energy system. The ability of the foundation, walls and roof to isolate occupants from outdoor conditions significantly impacts the operation of HVAC systems. Windows, doors, skylights and other apertures impact interior lighting and ventilation conditions in addition to heating and cooling demands.

    The building envelope, lighting, and HVAC systems should work together to optimize energy efficiency and provide a comfortable, pleasant environment for employees and customers. For example, high efficiency lighting reduces air conditioning costs since less heat is generated in the building by the high efficiency lighting.

    If the building envelope is "tight," the outside temperature fluctuations will have less impact on the building HVAC systems which work to maintain indoor temperatures. In Southern California, however, buildings can also take advantage of typically mild ambient conditions. In fact, for many commercial buildings the HVAC systems primarily work to remove interior heat (from occupants, lighting, and equipment) from the building. For these buildings, a well-insulated "tight" envelope will actually increase HVAC energy consumption.

    Building Envelope and Energy Use
    The building envelope can waste energy in four basic ways:

    Air Leakage . Conditioned (heated or cooled) air leaking out of the building, or outside air leaking in, through surface cracks and openings around windows and doors can dramatically increase the amount of energy needed to operate HVAC systems in order to maintain building comfort.

    Poor Insulation . Heat transfer into the building in summer, and out of the building in winter, through window glass or poorly insulated walls, ceilings and doors can also increase the amount of energy needed to operate HVAC systems.

    Ventilation and Humidity . The building envelope plays an important role in the ventilation of the building, that is the movement of air and moisture in and out of the building. The envelope should be designed in conjunction with the ventilation system to prevent excess condensation on windows and walls that can cause mildew and rot problems.

    Excess or Insufficient Sunlight . Good envelope design can allow the sun's light and heat in when desired, and deflect them when unwanted. The building envelope influences the artificial lighting systems and HVAC equipment sizing needed to maintain comfort in the building.


    Reducing Energy Use
    There are several inexpensive ways to reduce energy usage due to building envelope problems. The ideas detailed below fall into the general strategies of:

    1. Reducing air infiltration.

    2. Reducing heat transmission.

    3. Controlling humidity.

    4. Controlling sunlight.

    No-Cost Opportunities

    Isolate Unused Areas
    Closing HVAC dampers and sealing exterior windows can isolate spaces that are not occupied by people and may not need space conditioning. Isolating unused areas of the building results in a reduction of the total conditioned space and the energy used by the HVAC system.

    Door and Window Frames
    Tightening window and door frames will ensure that they are closely attached to the building and minimize unwanted air leaks. Automatic door closers should be periodically adjusted to ensure that they close the door completely and rapidly.

    Low-Cost Opportunities

    Seal Cracks
    Cracks may occur in foundations, walls, roofs and around apertures (windows, doors, and skylights) as well as flue chases, pipes and conduits leading into the building. Normal use, thermal expansion and contraction, material aging, foundation settling, or seismic damage can cause these cracks. Sealant caulking will eventually dry out and separate from building material surfaces. A variety of glass fiber, expanding foam, silicone and acrylic products can be used to repair cracks or restore damaged seals in the building envelope.

    Install Air Conditioner Covers
    Placing exterior insulating covers on window-mounted air conditioners during winter months will prevent air leakage both through and around the unit.

    Install Weather-stripping
    Installing rubber blade or brush-type door sweeps on the bottoms of exterior doors, or rubber weather-strips on thresholds, will limit airflow beneath the door. Rubber strips can also be used between double doors. Weather-stripping can be added around doorframes with metal or plastic "V" strips or adhesive-backed foam strips. Operable windows, particularly double-hung windows, may also benefit from the installation of thin foam weather-stripping.

    Window Repairs
    Broken or cracked windows should be repaired as soon as possible. Heavy gauge transparent tape can be used as an interim measure.

    Shading Devices
    Installing interior operable shading devices (blinds and shades) gives building occupants the ability to deflect direct sunlight when it is undesirable. This will reduce unwanted glare and temperature buildup in the building.