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Old House Beauty, New House Performance

Six important steps to making old houses more energy efficient.

There is something about old houses that definitely attracts people. Whether it is the history behind them, the eye-catching architectural details, or the sturdiness of the construction, old houses have an inexplicable charm that simply compels some people to fall in love, buy and restore them.

For many years, the people buying and restoring these properties felt no need to perform energy-efficient retrofits, because cooling and heating were still reasonably affordable and there wasn’t a lot of data on the environmental impact of home energy waste.

Today, a mix of soaring fuel prices, environmental concerns, and economic challenges have made home energy efficiency an urgent priority. Owners and buyers of old houses, especially those with historic value, are faced with the challenge of retrofitting them to reduce energy consumption, while taking every precaution to preserve architectural and historical integrity.

The good news is that virtually every old and historic house can be made energy efficient.

Fortunately houses are not like cars. While you can’t install a new hybrid engine in a classic car without taking away its value, you can transform an inefficient old house into a “lean, mean, energy-saving machine” without disfiguring it. Energy-efficient retrofits can make an old house perform just like a new green home, and as an added bonus, increase property value.

 Below is a step-by-step guide on how to transform an inefficient old house into a green historic property that is valued for energy performance as well as historic appeal.  

Step 1 - Get an Energy Audit

If you are serious about making your old house more energy efficient, before you tackle any actual improvement, get a home energy conservation specialist to perform a full home energy audit.

An experienced home energy performance specialist is sure to point out that your house is a system, comprised of smaller systems that work together. The energy-saving improvements made in one area will inevitably have an effect on other areas. A detailed energy audit will help you understand how your home uses and wastes energy, enabling you to make the right decisions to eliminate waste and optimize energy usage.

Using diagnostic tools and procedures like a blower door test and thermal imaging, an energy conservation specialist can detect air leakages, home insulation gaps or areas with insufficient insulation. Based on their report you can then build your plan of action, prioritizing the improvements that will make more sense to you in terms of energy savings and cost.

Step 2 - Attics and Basements

Building scientists –the experts who study all aspects of building performance—have established that a great deal of energy loss occurs in houses because of a phenomenon known as the “stack effect.” Basically, this occurs when the warmest air in the house rises naturally by convection and leaks out of the living space, into the attic and outside. This air loss creates negative pressure inside the house that causes exterior air to be drawn into the house through lower gaps and cracks. This combination of conditioned air leaking out while outside air leaks in is a major cause of poor energy performance.

In an unimproved house, the stack effect is happening non-stop, year round, causing your HVAC system to work much more than it should to maintain comfortable temperatures in the living space.  

The air that is moving about also carries moisture, and when that humid air cools down, or finds a cold surface, condensation occurs, creating mold problems in the basement, crawl space and attic.

Even if you don’t intend to use your basement your attic, these spaces should be professionally air-sealed to eliminate as much air leakage as possible. This air-sealing work is the only way to short-circuit the stack effect and stop unwanted air exfiltration and air infiltration.

If you live in an area where summers are hot and air-conditioning systems need to operate frequently, consider installing a radiant barrier in the attic. Whether you install this membrane as a plastic sheet material or a silvery paint, a radiant barrier will reflect some of the sun’s radiant energy so that your attic space will be cooler. Lowering the attic temperature during summer months will help lower your AC bills.

Like the attic, basements and crawl spaces should be thoroughly air-sealed. A vented crawl spaces is a huge energy waster, specially if you have ducts running through it. The energy loss can be enormous. If you have a crawl space, consider having it fully encapsulated and insulated. In addition to improving your home’s energy performance, this treatment , will also keep mold, dry rot and pests from compromising your home’s structural integrity. You can learn more about crawl space encapsulation at dirt-crawl-spaces.org.

With a basement or crawl space, a combination of air-sealing and insulation is the best way to ensure optimum energy performance. This is especially true if you live in a colder area of the US and Canada.

Step 3 – Adding Attic Insulation 

After the attic has been air-sealed, the next step is to insulate the attic properly. Installing extra insulation to the levels recommended by the U.S. Dept. of Energy will make a huge difference in the comfort and energy performance of your house just about all year round. 

An energy auditor may choose to use a thermal imaging (infrared) camera to locate attic areas that need more insulation. However, most houses don’t have adequate levels of insulation, so it’s a pretty sure bet you need more. An experienced home energy specialist will be able to recommend the best type of insulation based on the size and design of your attic space. Flooring installed in the attic for the purpose of storing things can limit the amount of extra insulation that can be installed. If you use your attic for storage, be prepared to move some stored items or talk to your energy performance specialist about building a new storage platform that provides clearance for extra insulation.

Step 4– Solving the Window Dilemma

Replacing existing windows for new energy efficient ones in old and historic homes usually poses a challenge. Many of these windows are made in custom sizes, but most importantly, they often have custom woodwork and details that are an important part of the house’s historical character. Replacing them with standard vinyl windows would, most likely, take away some of that architectural appeal.

The good news is that in many cases, you do not need to replace them at all, especially if they still function properly and aren’t damaged by rot. .

Heat loss through windows actually represent only 10%- 20% of a house’s total energy loss. Also, most of the energy loss occurs not on the window itself, but through air leaks between the window frame and the wall framing. So by caulking and sealing these leaks, replacing broken panes and, reapplying the putty, you can reduce that energy loss significantly –and save a huge amount of money compared to what you’d pay to install replacement windows.

What about the window itself –the sash, frame, stop moldings and other parts? A skilled carpenter can fully restore historic windows, bringing their energy performance much closer to that of new windows than you’d imagine.

In colder climates, a storm window can add an extra layer of protection and energy efficiency, while keeping the old windows intact.

Step 5 – Improving the Ductwork System

Many older houses with forced-air heating and/or cooling systems have dirty, leaky uninsulated ducts that waste a lot of energy. Leaky, uninsulated ductwork can diminish HVAC system performance by as much as 40%.  

The hard done by bad ductwork isn’t limited to energy loss. Leaky ducts can contribute to indoor air pollution and pose a serious health hazard to family members.

Dirt in the ducts can cause HVAC system failure and bring undesirable pollutants into the conditioned area of the house. Pressure imbalances caused by leaky ducts can cause backdrafting in combustion appliances, increasing the risk of exposure to carbon monoxide, a deadly gas. To avoid these undesirable consequences, it’s necessary to have ducts professionally sealed and insulated, and to have ducts cleaned periodically.

Step 6 – Upgrading HVAC Systems

After taking every step to make sure the house is more airtight and better insulated, it is time to look at the HVAC system.  

There are many different types of HVAC systems. Some houses have furnaces, while others have boilers or heat pumps. Regardless of what HVAC components you’re dealing with, older equipment will never operate as efficiently as new ENERGY STAR™ equipment. A gas or oil-burning furnace that’s more than 15 years old may be working perfectly, requiring only regular maintenance that costs very little. But even in perfect condition, this furnace will only be around 60% efficient at converting fuel into heat. A new ENERGY STAR™ gas furnace, on the other hand, can work at 90% efficiency. These same differences in efficiency exist for heat pumps and boilers.

It my not be in your budget to upgrade the HVAC system after investing in all the other energy-saving improvements mentioned above. But when you do elect to replace an old HVAC system, your new system can be smaller because your home’s building envelope is now more airtight and better insulated. The reward for your insulation, air-sealing and duct-sealing improvements is a less-expensive downsized HVAC system with lower energy requirements.

With proper expertise and guidance, you can restore and preserve your old house and all its historic beauty and character, and have it perform as well as a 21st century home. 

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