Modern heating and cooling upgrades for old houses

In the course of my work as a New York City home and building inspector, I see brownstones and other old buildings modernized for 21st century life without serious consideration given to modern, energy-efficient heating and cooling alternatives. There are two main reasons for this lack of foresight. First, there is cost consideration, as energy-efficient modern equipment is often more expensive than its conventional, less-efficient counterparts. Second, the contractor doing the work may not be familiar with the newer options in the HVAC marketplace. Very often both reasons are at hand. Such decisions are lost opportunities because such equipment would remain in place for many years, even decades. With respect to the first consideration, it is important to note that energy savings on ultra-high-efficient equipment can be expected to pay for itself multiple times over the life of the equipment when you compare to the efficiencies of conventional equipment. For example, if you switch from an oil-fired to a gas-fired heating system, the payback period is fairly short because in today’s market, oil costs around twice as much as gas to produce the same amount of energy, not to mention the responsibility of keeping oil stored on the property. Regarding the second consideration, many, if not most, contractors prefer to avoid learning curves and stick to what they know. Learning curves cost money in the form of time spent on callbacks as well as the training that is often required to install and service newer technology. There is also fear of the unknown and mistrust of new-fangled equipment that is not perceived in their minds to have any track record. You may want to reconsider the hiring of HVAC contractors who only present options for 20th-century-style equipment. **The chimney: a lingering vestige of earlier times** Chimneys were originally used in brownstones and other 100+ year-old houses to vent hot gases and smoke from wood-burning fireplaces, which were the primary space heating sources when those buildings were new. Chimneys were made of brick because the gases from the fireplaces were very hot. Eventually, wood as a fuel source was replaced with coal, coal was replaced with oil, and now oil is being replaced with natural gas, although plenty of oil-fired heating equipment is still out there. The chimney hasn’t changed over all these years: its purpose is still to carry hot fumes from wood, coal, oil, and natural gas out of the building. And with the exiting gases goes what we refer to as WASTE HEAT. Heating equipment has a standardized efficiency measurement called Annual Fuel Utilization Efficiency (AFUE). It is a measure of how much of the input fuel actually gets utilized for space heating over the course of the season as compared against waste heat that goes up the chimney. So if a boiler is rated at 80% AFUE, 20% of the energy you purchase goes right up the chimney as waste heat. Anything older than 20 or 30 years probably has an AFUE more in the range of 65% – 75%. That was fine when heating costs were not a concern. Needless to say, things have changed. Far more often than not, I find that chimneys are in quite poor condition after having been in use for over 100 years with nary a thought. An in-use chimney in poor condition is at high risk of being both a fire and health hazard. They can cost several thousand dollars to restore. Clay-lined or unlined chimneys that have been venting natural gas equipment for a long time can be at imminent risk for internal collapse, as natural gas combustion produces lots of moisture, which is acidic and corrosive to masonry. Such chimneys would best be lined with a metal sleeve (flue liner) for continued safe operation. **Enter: Condensing equipment** However, the goal for the 21st century is not to restore or reline the chimney, but to eliminate it altogether by utilizing modern gas-fired condensing equipment. Gas-fired condensing equipment is designed with a longer heat exchanger so that much more (almost all, in fact) of the heat from combustion gas is captured into the distribution system rather than wasting to the outdoors through the chimney. This equipment has AFUE efficiencies that can exceed 95%, so instead of a chimney, the gases can exit the building through a plastic (PVC) pipe called a direct-vent. The outgoing gases are around 90º – 100ºF, cooler than a hair dryer. These units can also draw their own combustion air directly from the outside through another PVC pipe, in a setup called sealed combustion, so that there’s no need for a fresh air opening in the heating area. These features allow for many more location options, so you’re not relegated to installing equipment in the basement, or even by an exterior wall. You can have a mechanical closet on any floor. Condensing systems can take the form of a forced-water boiler (with baseboard radiators and/or radiant heat) or a forced-air furnace (with air ducts that can be multi-purposed along with central air conditioning). Boilers are made now that are quite small and can hang from a wall, providing double duty by generating domestic hot water for the faucets and well as space heat. Direct-vent, sealed combustion water heaters are available as well. Condensing equipment has been in the local marketplace for over 20 years and has an established track record. Although there are new condensing oil-fired systems out there, venting still needs to be done with metal and fresh air often needs to be available to the heating area. This limits installation flexibility. Given that and the unfavorable comparison of oil to gas costs, switching to gas is still the better alternative. Side note: It is worthy to mention that I often see old buildings with oil-fired forced water systems that need a new oil tank and chimney restoration. These costs of concern can be entirely eliminated by upgrading to a gas-fired condensing boiler. Since it’s money that needs to be spent anyway, it is best invested in modern equipment, rather than a dying paradigm. **Steam systems** Many brownstones, row houses, and other old buildings have steam systems, characterized by the test-tube-like sight glass on the side of the boiler, large diameter steam pipes, and big, hot cast iron radiators. Unfortunately, high-efficiency equipment options are not yet available for steam systems. The best thing you can do is switch from oil to gas. To maximize the performance of a steam boiler, it should come equipped with an electronic ignition instead of a standing pilot light, which burns gas 24/7\. It should also have a motorized stack damper that closes automatically when the flame goes out, to minimize heating losses up the chimney when the boiler is not firing. Make sure all the steam vents on radiators and mains don’t hiss or leak steam. Be prepared to reline the chimney if the boiler is in an old building. Switching to a forced-water system in order to take advantage of condensing equipment is a noble but costly proposition, as all of the pipes and radiators should ideally be replaced. This is easiest done during a gut renovation. Steam radiators get very hot to compensate for the air leaks in the building shell, poor quality windows, and lack of insulation. Since forced-water radiators don’t get as hot, upgrades to insulation and windows should be considered as part of such a renovation to assure comfort for building occupants. **Air conditioning** Standard ducted central air conditioning systems consist of three components: an air handler (to condition air and move that conditioned air around the building), ducts (to carry the air), and a condensing unit (the large box with the fan located outside, responsible for rejecting heat from the building). Retrofitting ducts can be difficult, especially in row houses, and they often end up within soffits that some may consider less than aesthetic. Ducted systems have inherent shortcomings, especially when retrofitting to an old building. It has been demonstrated to me over and over again that many, if not most, HVAC installers do not do a good job of sealing ducts. This is a problem in unconditioned basements, attics, and other interstitial spaces resulting in leaking of conditioned air to these spaces on the supply side, as well as drawing in of unconditioned air into the system on the return side. Either one of these outcomes results in energy losses. Condensation in unwanted places can also result from poorly sealed ductwork. Cooling losses are often compounded by installation of ductwork and air handlers (cooling equipment) in the hottest place in the house — the attic. Someday this will be a building code violation, but today it’s the way things are done. Counterintuitive? You bet! HVAC installers make up for these shortcomings by oversizing the cooling equipment. This will prevent callbacks for the installer, but it is a disservice to the homeowner and over time can result in visible condensation problems from cool damp air and premature compressor failure from short-cycling. Ducted systems are often installed and maintained with insufficient filtration, resulting in crud buildup inside the ducts and bio-slime (basically, mold) buildup on the evaporator coil in the air handler cabinet, which is often ignored for years. Note that this bio-slime is in the air stream, so your interior space gets peppered with mold spores. **Mini-split systems** A great A/C alternative for old houses, especially row houses, is the mini-split system. You may have seen these systems in offices or restaurants. The interior end takes the appearance of a short, wide, high up wall unit that blows cool air. These units are tied into an exterior condensing unit. One condensing unit can drive up to 4 wall units. Mini-split systems have tremendous advantages over conventional cooling equipment. They are ductless, which means no transmission losses, ugly duct soffits, and complicated installations. It is much easier to run refrigerant piping as opposed to ductwork. Wall units do not have to be installed on exterior walls, which provides more options. They can be installed anywhere as long as they can drain the condensed water, which is the humidity pulled out of the air. One or two strategically located wall units can cool an entire floor of a brownstone. They are super-efficient and super-quiet, with efficiencies far exceeding conventional wall A/Cs or central A/C. Each wall unit is controlled independently with its own remote. And they can also include optional heating mode. State-of-the-art inverter heat pumps can operate well in temperatures down to -10ºF. So even if your building has a central heating system, the mini-splits can be used as spot augmentation or as backup in the event of central heating system failure. **Matt Wynne** [AberdeenBuildingConsulting.com](http://AberdeenBuildingConsulting.com “Aberdeen Building Consulting”)