Editor's Note: This energy audit was conducted on our house as part of our 70s house eco renovation project to help us prioritize weatherization and energy efficiency projects. This is one in a series of articles documenting the eco renovation of our house. See the links at the bottom of this article for other articles in this series.
Dear Mr. Barbalace:
At your request, we performed a full energy audit of your property on Aug 7th, 2009. This full audit was for the purpose of qualification for the Maine State Housing Authority (MSHA) Home Energy Loan Program (HELP) loan program. The report which follows was based on that assessment. The audit was made using the weatherization, insulation and ventilation standards defined in the Department of Energy's Northeastern Weatherization Field Guide, EnergyStar's Insulation Guidelines and ASHRAE 62.2 (American Society of Heating, Refrigerating and Air-Conditioning Engineers) respectively.
Free Energy Maine, LLC offers two levels of residential energy assessments; the Basic Audit and the Full Audit. The Basic Audit entails a complete infrared scan and visual inspection of the property's thermal barrier and air infiltration issues. The Full Audit includes a blower door test and full collection of insulation and housing dimension data. A Full Audit is required to quantify home energy loss and make accurate Return on Investment (ROI) calculations for the HELP loan.
Your energy assessment was performed by and this report was written by Erik North, owner of Free Energy Maine, LLC.
Free Energy Maine, LLC P.O. Box 1247 Westbrook, ME 04098 Tel: (207) 329-7219
This report has been prepared looking at all aspects of the home's energy efficiency. Thus, many of the items discussed may go beyond the scope of immediate concerns and are mindful of the larger plans for the home.
This home energy assessment revealed substantial heat loss because of an incomplete attic thermal barrier. The open stairway to the attic bypasses the insulated attic floor. This causes the uninsulated interior walls around the stairwell to be the barrier between the interior heated space and exterior unheated space. There was also significant heat loss through excessive air leakage, the uninsulated basement walls and poor insulation performance in the main living space walls. Other shortcomings typical of home construction practices circa 1971 offer several energy saving opportunities as outlined in the "Recommendations" section of the report.
The residence was built in approximately 1971 and is a single story platform framed home with an unfinished full basement and an unheated attached garage. The home has a oil fired, hot water boiler with an indirect hot water tank.
Free Energy Maine, LLC performed a visual energy performance inspection, infrared scan and blower door depressurization testing of the property.
|Area sq/ft||R Val||ACH||Effic||Vol cu/ft||Heat Loss Therms||Annual Cost @ $2.5/gal|
|Air Heat Loss||1.43||9120||413.4||$1,033.53|
|Stand-by Loss (Assumes 10% distribution loss)||144.0||$360.00|
From the energy modeling of the house, the greatest losses are from air leakage and radiant heat loss through the attic and basement.
While the walls and ceilings are reasonably insulated, they fall well short of current standards and should be upgraded.
* Note that all surfaces were modeled individually and the heat loss, R-value and area are composite values.
EDITOR'S NOTE: These numbers are based on guestimations of how much different tasks would cost to complete and some numbers assume that work would be done by home owner (e.g. me). Please make sure to see the updated ROI, which was calculated based on actual quotes and taking into account new building code requirements.
|R Val||ACH||Effic||Heat Loss Therms||Proposed Action||R Val||ACH||Effic||Heat Loss Therms||Pay Back yrs||ROI %|
|Attic||7||360.4||Adding Cellulose Insulation||48||42.7||2.5||39.7%|
|Air Heat Loss||1.43||413.4||Air Sealing||0.50||144.2||1.5||67.5%|
|Heating System||81%||Propane Condensing Boiler||94%||11.5||8.7%|
|Hot Water Stand-by Loss||144.0||Propane Tankless Hot Water||61.0||2.9||34.6%|
|Basement Walls||2||176.1||Insulate Walls*||11||32.0||2.8||36.0%|
|1st Floor Walls||10||172.6||Injected Foam||22||78.5||17.0||5.9%|
|Injected foam w/Building Wrap||40||43.2||24.7||4.1%|
|Windows||2||88.2||Replace w/ Low-E II Windows||4||44.1||63.5||1.6%|
From the return on investment calculations, the best investments are in air sealing, insulating in the attic and the basement. However, replacing the heating system and insulating the walls are also worth-while investments. Replacing the windows and doors would result in milder energy savings. Given the considerable expense and relatively modest R-value increases, window and door replacements should be considered after other measures.
This section is an overview of possible ways to decrease your home energy bills. They are rated on their cost benefit from 1 to 5: Low, Modest, Average, Good and Superb. The ratings are determined by the savings of the repair versus the estimated cost.
The attic is currently insulated with foil-backed fiberglass batts. The insulation seems to be performing adequately but is well short of current standards for attic insulation.
The true performance issue in the attic is the open staircase, a direct path for air leakage and heat loss through the building envelope. Effectively this causes the uninsulated interior walls and attic access door to be part of the attic's insulation barrier. Thermally, this is like having an equivalent hole in the home's ceiling covered with a sheet of plywood.
The enclosed storage space in the attic is performing significantly better than the rest of the house. When making decisions about the attic insulation, take into account that the room has been insulated to a higher level than the rest of the house.
There is substantial area for reducing air transported heat loss with relatively little expense. The house tested at 3900 ft3/min (CFM) when de-pressurized during the blower door testing. This is significantly in excess of the necessary ventilation as laid out in ASHRAE 62 & 62.2. The major sources of air leakage were the basement sill plate, the attic entry, the chimney stack and interior partition walls leaking from the attic into interior spaces without an air barrier (ex., closets with wood partition walls rather than plaster). Other areas of note were the unused front door, the non-working mudroom door and the older basement windows. The main mudroom door, the living room bay window, the rear sliding door and all the main floor windows showed expected but not excessive levels of air leakage.
The decision to perform any of the detailed air sealing work should be considered in the larger plan for the home. For example, if the homeowner decided to insulate the walls with injected foam or densepacked cellulose in the future, this would achieve all the needed wall air sealing.
Unless otherwise noted, all air-sealing should be done with low expansion foam sealant and pure silicon caulking.
EDITOR'S NOTE: Potential savings from insulating foundation walls were significantly reduced by unexpected requirement to install 15minute sheet rock fire break over all foam insulation. This would have more than doubled the costs of insulating foundation walls. Please see revised ROI calculations for more details
There is also a substantial opportunity for savings by insulating the basement walls and sill plate/band joist. Concrete and granite foundations have almost no heat retaining ability (1 foot of concrete has the same insulation factor as a single pane of glass). Additionally, controlling basement moisture is essential to reducing overall building humidity levels. The combination of insulation, air and water sealing will help save money, ensure the buildings durability and contribute to healthier humidity levels.
There was some water staining caused by leakage from the heating system. However, there was no evidence of standing water or efflorescence (mineral salts left by evaporating water) on the walls. The basement's observed relative humidity on the day of the audit was 65% when exterior humidity was 54%. This indicates that a significant level of water vapor is evaporating into the house from the foundation.
All of these recommendations refer to both the main basement and the extension crawlspace.
An oil-fired, forced hot water system heats the house. This unit consists of a burner, a boiler (in which the water is heated) and a circulating pump to move the water through the system. There was an attached water storage tank.
The boilerplate and the documents located on site indicate that it has a maximum heating capacity of 152000 BTU/hr, which is significantly over the expected heat load of the house. The same documents indicated it was installed in 1990. A high-mass hot water boiler would normally have a service life around 25 years. However, this unit is leaking and there is considerable visible corrosion.
The heating system tested at 81% efficiency. This is below current minimum Energy Star standards and given the poor condition of the boiler, significant work would need to be performed to bring it to optimal performance.
The distribution system (hot water pipes and baseboard units) are currently partially insulated with fiberglass strips. Typically 10% of the delivered heat is lost during distribution (for example, if a house used 1000 gallons of oil, 100 gallons worth of heat would be lost). The hot water operates off the heating system and is stored in a SuperStor tank installed at the same time as the boiler.
Given that both systems are late in their service life, they are candidates for replacement.
The walls are an instance where the remodeling plans of the house need to be weighed with the current energy plans. The walls of the structure were standard platform framed 2x4" construction insulated with the same foil back fiberglass as in the attic. From the IR scan the wall insulation is performing adequately through there was some evidence of gapping and settling. By either injecting either foam insulation or when remodeling, replacing the fiberglass insulation with spray foam insulation substantial savings can be realized. Either measure would also air-seal the house.
The house currently has double paned replacement windows and newer insulated core doors. These is a glass double sliding deck door in the rear of the house and a three paneled single pane bay window in front.
At this time, there would be no benefit in replacing either the doors or windows with more efficient versions given the cost. A lower cost option to consider would be insulated window treatments (make sure they are the type with magnetic tape to form an air-tight seal).
There is significant room for savings with many reasonable options for the homeowners. As stated, air-sealing the entire structure, insulating the basement and clearly defining the thermal barrier and insulating in the attic will be the most cost effective measures and offer the greatest potential for savings.
ACH is an acronym for Air Changes per Hour and is a measurement of air infiltration. It is the total volume of air in a home that is turned over in one hour. There are two methods for calculating the ACH, using either the Building Air Flow Standard (BAS) or Occupancy Standard determined by the number of bedrooms + 1, assuming a master suite with two occupants.
The higher of these numbers is used as multiplier to determine the Minimum CFM50. Should any changes be made to either of these variables a new minimum would have to be determined.
British Thermal Unit. A measure of heat equal to the amount of energy to raise 1 pound of water by 1 degree Fahrenheit.
The CAZ is the area that houses the appliances that heat the home through combustion, such as a boiler or a gas furnace. Typically located in the basement, they can also be located in other areas such as garages or portions of the main floors. The CAZ needs to maintain a minimum pressurization to avoid spillage, back drafts, or other hazards.
In some instances the amount of mechanical ventilation running in the home can depressurize the CAZ too much for the appliances to maintain proper safety specifications which are currently -3 to -5 Pascals (Pa).
This is the airflow (in Cubic Feet per Minute) needed to create a change in building pressure of 50 Pascals. CFM50 is the most commonly used measure of building airtightness and represents a fictional winding blowing on all sides of the structure at approx. 20 mph.
It is possible to increase the airtightness of a building to the point where natural air change rates (from air leakage) may not provide adequate ventilation to maintain acceptable indoor air quality.
To help evaluate the need for mechanical ventilation in buildings, national ventilation guidelines have been established by ASHRAE. The recommended whole building mechanical ventilation rate presented here is based on ASHRAE Standard 62-2003, and is only appropriate for low-rise residential structures.
These are an approximation of the costs to effect the repairs suggested (including labor). The actual costs will depend on the individual contractors.
This is the equivalent use of fuel burned determined by calculating the heat in BTUs needed to heat a cubic foot of air.
Heating load is the maximum number of BTUs the heating system will need to provide for a comfortable interior temperature. The load is calculated on a worst case scenario (in other words, the coldest it is likely to ever get in your area). Losses after repair: The amount of energy losses after suggested repairs Mechanical Ventilation Requirements: This is the amount of air needed to maintain the Minimum CFM50. It can be achieved through a variety of means such as an exhaust fan or Heat Recovery System, but is needed to maintain occupancy and building safety.
The amount of energy losses at current conditions.
The amount of heat resistance currently in the component.
This is the amount of time it will take to recoup the costs vs. savings. (Costs/Savings)
1/250th inches of Water Column. A unit of pressure in the meter-kilogram-second system equivalent to one newton per square meter
This is the return on the dollar for money spent. (Savings/Costs)
This represents the amount of money to be saved in current dollars at the current price of the fuel being used by the structure.
The amount of resistance that can be achieved.
This is a metric used by banks to determine the feasibility of a repair before offering loan money, usually. It is the ROI multiplied by the number of years the repair will be in effect, usually standardized to 30 years.
100,000 BTUs. Often used to standardize the comparison of different energy sources. When used for home heating and hot water, natural gas is delivered in therms. Units: The unit in question is determined by how one heats their home. For oil and gas the unit would be gallons, for electric heat, kilowatt hours (kwH).
If you need to cite this page, you can copy this text:
Erik North, Free Energy Maine, LLC. 70s House Eco Renovation - Initial Energy Audit. EnvironmentalChemistry.com. Oct. 14, 2009. Accessed on-line: 9/27/2020