Replacing Furnaces & Air Conditioners

This question was posed on a community-networking site in the San Francisco Bay Area. I thought it would make a great topic for my new post, so here goes!

“It looks like we are facing replacement of our furnace and air conditioner soon. I’m sure that a number of residents have done a thorough exploration of what the most energy efficient HVAC systems are available on the market. I would love to tap into the collective wisdom and find out what you have discovered.”

The ‘Systems-Approch’ – A Critical Principle of Sustainable Design & Green-Building

Green Remodeling is really a ‘systems-approach’ to doing the things all homeowners have needed to do since, well – becoming Homeowners, like upgrading, replacing, maintaining all parts of their most valuable asset. By systems-approach, I mean that a building functions much like our body. There are various systems that need to be integrated and balanced to function most effectively. When one system, like the HVAC (heating, ventilating, air conditioning) system, or in our bodies, the nervous system, is impacted, it affects the other systems, as well.

This means that when replacing your furnace and air conditioner, if you want to get the most in regards to energy efficiency, you need to look beyond just the equipment. Buying a 90% efficient furnace and installing it in a ‘leaky’ house is not only a waste of money, but a waste of energy – your energy and that which you are trying to use to increase the comfort of your home.

So, along with researching the most energy-efficient equipment on the market, you need to be aware of building physics, and how an energy-efficient home performs – and make sure your home’s systems will function in the most integrated and balanced way.

The First Step: Get a Home Performance Assessment by a Qualified, Certified Professional

A certified professional will perform an extensive audit by pressurizing the home and using specialized equipment to discover where the conditioned air is leaking out, and where the unwanted outside air is coming in. The auditor will also conduct a Standby and Operational Loads Analysis and recommend strategies to increase energy-efficiency, like sealing of penetrations to the thermal barrier, replacement of leaking, uninsulated heating ducts, and installation of attic, wall, and water line insulation. These are all relatively low-cost ‘upgrades’ that can have big results in the overall comfort of your home – and your new furnace will work much more efficiently.

At Spectrum Fine Homes, the remodeling company I co-own with my husband, Bob Davis, we believe in using a ‘third-party’ Home Performance Specialist. We have been working with Suzanne Emerson, Emerson Environmental for the past couple years. The report she gives to the homeowner is comprehensive, and offers suggestions and options that are tiered in complexity of implementation.

Some HVAC contractors offer this service, too, but I think having a ‘third-party’ professional do both a ‘Test-In’ and a ‘Test-Out’, after the ‘retrofitting’ is finished, is your best assurance that things are done properly.

Implementing Strategies to Increase Energy-Efficiency & Comfort

For implementing the options that require help beyond the homeowners’ capabilities, we recommend using licensed, certified, and insured professionals. If there are three or more things needing to be addressed, (like sealing penetrations, insulating, new HVAC system, electrical, plumbing, drywall or painting work) we highly recommend using the services of an experienced, licensed, certified, and insured General Contractor to professionally coordinate and manage the project.

A good GC will have a team of reliable and expert ‘Trade-Specialists’ to perfectly match to the needs of your project, and will assure that the job is done right and in a timely, professional way. Great project management skills and experienced professionals will make the experience of having work done on your home as pleasant and stress-less as possible.

The HVAC System – Options You May Not Have Considered

I’ve mentioned 90% efficient furnaces a couple times. What, exactly, does this mean?

The most important thing to remember is that your new furnace needs to be properly sized utilizing ‘load-calculations’ based upon the results of the Home Performance Assessment and the suggested strategies that you’ve now implemented (sealing air penetrations, adding attic insulation, etc.)

An oversized furnace (one whose capacity is too large) costs substantially more to operate than a correctly sized furnace. This is because oversized furnaces will cycle on and off more often than correctly sized furnaces. Cycling on and off is more expensive than running at steady state. High efficiency furnaces cost more than average and low- efficiency furnaces. However, they tend to cost less to operate on a month-to-month basis as they use less fuel to generate the same amount of heat. Therefore, after a given payoff period, high efficiency furnaces tend to cost less than low efficiency furnaces. (One of the things I love about Suzanne Emerson’s reports, is that she includes this cost/benefit analysis for a 90% efficient furnace, and you can determine whether it’s worth it to you to invest in this kind of equipment.)

A properly designed HVAC system is critical, too. I’ve seen many homes with two furnaces where really only one was needed. A good HVAC ‘Trade-Specialist’ can design an efficient, zoned, system, with equipment sized to accommodate the specific needs of your home. Just buying equipment off the shelf and plugging it in isn’t the best way to maximize energy efficiency and comfort, or your budget.

A traditional gas fueled furnace/AC unit is only one option to consider. There have been some exciting HVAC innovations in the last several years. Consider installing a solar- thermal system that both heats your domestic water supply – and with the use of a heat-exchanger connected to a high-efficiency water-heater like the Phoenix , can provide heat through your existing heating ducts. This is a great option if your water heater is approaching the end of its lifetime, or you’ve been considering a solar- thermal system. Solar-thermal installations require less sun than photovoltaic (electricity producing) systems, and are less expensive to engineer, purchase, and install. Plus, the Stimulus Incentive 30% tax credit given for installing energy-efficient systems makes this option very affordable, especially when you consider the operating costs over the life of the equipment –  the cost of the ‘fuel’ (the sun) is free.

Don’t Forget the ‘V’ in HVAC

As your building envelope is tightened with the sealing of penetrations, the need for good ventilation becomes paramount. Many of the products and materials we bring into our homes potentially off-gas toxic chemicals into the indoor environment. These can include the ‘open-combustion’ equipment like some furnaces, gas fireplaces, and gas ranges, to furnishings, clothing, cosmetics, and cleaning products. Studies have shown that the indoor environment of our homes is often more unhealthy than outdoors! This definitely affects the health and comfort of our families and our homes.

The new California Title 24 Energy Code, implemented on January 1st, 2010, addresses this issue for new residential construction and major remodels. Code now requires properly sized, continuously running, mechanical ventilation in homes, so that unhealthy air is vented out, and fresh air is mechanically vented into the home. Calculations are required to determine adequate air-exchanges for the occupancy of the home.

Supplying proper mechanical ventilation is not difficult, and not intrusive to the function or aesthetics of your home. It can be accomplished by installing a properly sized Panasonic Whisper Green ventilating fan in a bathroom or laundry-room. This piece of equipment is so quiet that you don’t even know it is running, and is Energy Star Certified, so running it constantly doesn’t dramatically affect your energy costs.

My company, Spectrum Fine Homes, is offering a free Whisper Green ventilating fan to any new remodeling client – we so believe in the value and necessity of proper ventilation for both your family’s health and for the comfort of your home.

Again, balancing the systems of heating and ventilation, contribute to both energy efficiency and healthy indoor air quality. Remember – it’s all integrated.

Cooling Your Home

Living in the San Francisco Bay Area, we are blessed with a year-round temperate climate. Very rarely do our summer temperatures exceed 100 degrees, nor do we suffer with high humidity levels. The potential to ‘passively’ maintain comfortable indoor temperatures in the summertime increases when you give attention to the holistic, systems-approach to designing, building, and maintaining your home. T

he very first consideration should be how your home is oriented to the sun, the prevailing breezes, and to the natural environment of the site. Your home will get the most ‘heat-gain’ from the south-west exposure, so providing shade, either with plantings or with architectural overhangs or garden structures, can keep the interior of your home several degrees cooler in the warm months. If you have a lot of windows on the southwest side of your home, the type of window glass, as well as your choice of decorative window treatments can make a difference, too.

If your home is oriented to receive the prevailing breezes through open windows, especially, from a shaded, northern exposure, it makes sense to take advantage of the natural cooling effect of fresh air. I also like using skylights that open to create a natural convection effect, where cooler air comes in the windows and warmer air rises and escapes out the skylight. Placing the skylights with the correct orientation to the sun, and making sure that the windows open correctly so they don’t actually block the breezes, is important in passive cooling, too.

Hopefully, the changes you made to your home after the Home Performance Assessment included adding adequate attic insulation and sealing up any air leaks around penetrations into the attic from recessed light fixtures. In warm weather, attics can reach temperatures well over 100 degrees, and if your living spaces are not sealed and insulated, this hot air will be entering, and really affecting the comfort of your home. The addition of a ‘radiant barrier’ in the attic, and also using ‘cool-roof’ material choices, can also help keep your home much cooler and more comfortable.

You may also want to consider a ‘whole-house fan’ as part of the HVAC system. This piece of equipment can help keep your home cool instead of using a traditional air conditioner that cools the air that it blows through the ducts. The whole-house fan will bring in fresh air from the outdoors and mechanically vent out the warm indoor air. There is a good explanation of this type of system at http://www.wholehousefan.com/ Whole-house fans can provide the Title 24 code requirement mentioned earlier in this post, as well. They are also more energy-efficient and much lower in operating costs than central air conditioning.

With all these more ‘passive’ cooling options, you may not need mechanical cooling from a traditional air conditioner. But if you still want to go the central-air conditioning route, here are a couple considerations:

At the very minimum, make sure your ducts are sealed and well insulated. It makes absolutely no sense to chill air at the AC unit, and blow it through metal ducts in an attic that is 120 degrees. These metal ducts, through the physics’ principle of conductivity, will be over 100 degrees, and very quickly that chilled air will be warm air blowing through the vents into your ‘conditioned’ space. You are now uncomfortable AND paying extra utility costs for heating your home in the summer – and wondering why it’s so uncomfortable when you know you just installed a new air conditioner!

Air conditioners, like furnaces, need to be properly sized for the needs of your home. There is some great information on the Energy Star website about how and why air conditioners need to be sized.  If you’ve done the basic, low-cost, home improvements suggested in the Home Performance Assessment, you will be able to use a smaller, more efficient air conditioner, and save in both upfront equipment costs as well as in operating costs.

Parting Thoughts

Hopefully you will find some information here to help you make an informed decision about replacing your furnace and air conditioner. As you can see, I think it’s a much more involved decision than just choosing the most energy-efficient piece of equipment. I think it takes looking at things very holistically, understanding ‘building science’ and really taking the ‘systems-approach’ to understanding your individual home’s needs.

For more information check out Suzanne Emerson’s website, Resources section where she generously shares loads of informational downloads including some specific to Portola Valley. http://www.emersonenvironmental.com/resources.html

For more information about solar-thermal options see http://sunwatersolar.com/

For more information about Spectrum Fine Homes, Inc. and our WhisperGreen Ventilating Fan promotion contact us at http://www.SpectrumFineHomes.com and read the archived March Newsletter, here, on the GreenPointCoach blog.

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