First establish which kind of building you are in
Heating and cooling in a multi-unit residential building can be organised in fundamentally different ways, and which architecture the building uses determines almost everything else — what the association owns, what you control, what the failure modes are, and whether there is a Legionella risk at all. Nobody can answer "who is responsible for my heating" without first answering "what kind of system is this".
- Central plant with hydronic distribution. A central boiler and chiller produce hot or chilled water, pumped to terminal units in each dwelling — fan coils, radiators, convectors.
- Condenser water loop with in-unit water-source heat pumps. A moderate-temperature loop circulates through the building, each unit's heat pump rejecting heat to it or absorbing heat from it, with a cooling tower rejecting excess heat and a boiler adding it when the loop runs cold. Every unit heats or cools independently on two pipes.
- Self-contained equipment per unit — packaged through-wall units, split systems with an outdoor condenser, or VRF. The association's involvement is the sleeve, the structure and the electrical supply, and the awkwardness is owner-owned equipment sitting on the association's property.
One equipment choice cuts across all of it: an air-cooled chiller rejects heat directly to outside air and has no cooling tower, which removes the tower-related Legionella risk entirely. A water-cooled chiller uses a condenser loop and a tower: more efficient, and it introduces one.
Two-pipe versus four-pipe, and the complaint nobody can fix
A two-pipe system has one supply and one return serving every terminal unit, carrying either hot water or chilled water at any given time. The building must be changed over seasonally, and every unit is in the same mode. The consequence is direct: no owner can have heat while the building is in cooling mode, or cooling while it is in heating mode. On a warm spring afternoon or a cold snap in autumn, some units are uncomfortable and nothing can be done. Changeover is a disruptive management decision, and it generates much of the resident dissatisfaction in older hydronic buildings.
A four-pipe system has separate supply and return for hot and chilled water, so each terminal can heat or cool at any time independently. It costs more to install and needs both plants available, but it is markedly better for comfort and is standard in newer construction.
Converting a two-pipe building to four-pipe is a very large project: a second set of risers and branches through the building, which is the same access and disruption problem as a plumbing riser replacement, plus new terminal units everywhere. Associations study it and do not do it, so the honest answer to owners who ask is that the discomfort is a design characteristic rather than a maintenance failure. None of which makes a two-pipe building a bad building — it makes it a building with a known limitation, which should be priced and understood rather than discovered in October.
The plant, and what makes it obsolete
Chillers. Condenser and evaporator tubes foul, erode and eventually fail, with eddy-current testing the standard non-destructive assessment. But the dominant issue is not wear. Refrigerant transitions are the most significant obsolescence driver here, and the thing an association with an older chiller most needs to understand. Refrigerants have been phased out and down in successive regulatory waves — first ozone-depleting substances, more recently high global warming potential compounds. A machine running on a refrigerant being phased down faces rising service gas costs and eventual unavailability, forcing replacement on a regulatory schedule rather than a condition schedule. The schedule and the affected refrigerants change, so check the current position rather than any article's list.
Boilers. Sectional cast iron boilers crack, tubes and refractory deteriorate, and burners drift out of adjustment. Combustion venting deserves attention: in older buildings a chimney sized for a much larger original boiler is now oversized, which promotes condensation and decay, and combustion safety is a life-safety matter because of carbon monoxide. Boilers are subject to periodic inspection under state boiler codes, so records exist.
Cooling towers reject heat by evaporating water, and their components sit outdoors, wet, all season: basins corrode, fill scales and fouls biologically, and drift eliminators degrade, which increases the aerosol released to the surroundings.
Terminal equipment and ducts. Coils foul, filters go unchanged, and fan coil condensate is a major and underappreciated source of water damage — a blocked drain overflows into the unit and those below, which in a building with hundreds of fan coils happens regularly. Prevention needs a maintenance programme with access to every unit — as does cleaning the dryer exhaust ducts whose lint accumulation is a fire hazard where there is in-unit laundry.
Legionella: the part that is about health rather than comfort
The CDC frames the growth conditions as STAR: Sediment, scale and biofilm, which provide protected environments where bacteria survive disinfection; Temperature, with Legionella growing in the range 77–113°F (25–45°C); water Age, since stagnation allows biofilm to develop and disinfectant to dissipate; and disinfectant Residuals, where insufficient residual fails to suppress growth.
Where it grows in a residential building: cooling towers, the highest-profile source because their aerosol can travel from the roof to street level and into air intakes; hot water systems, with storage held within the growth range and recirculation loops with dead legs; showers and faucets, which produce the aerosol that delivers the organism to the lungs; and fountains and spas. Amenity areas make condominiums a specific case: a spa, a pool with water features, a fountain and a cooling tower are four independent amplification pathways in a building whose residents often skew older, and age is a major risk factor. Seasonal vacancy is a second condominium-specific amplifier, since units left empty for months leave the water in those branches stagnant at building temperature.
The governing framework. ANSI/ASHRAE Standard 188, Legionellosis: Risk Management for Building Water Systems, is the consensus standard. Its 2021 edition sets minimum risk management requirements for building water systems, and its scope applies to human-occupied commercial, institutional, multi-unit residential and industrial buildings, excluding single-family residential buildings. That explicit inclusion of multi-unit residential buildings is directly on point for condominiums.
The instrument the standard turns on is a water management program, and the CDC publishes a toolkit for developing one: a team with defined responsibility; flow diagrams of where water enters, is stored, heated, distributed and released as an aerosol; control measures with defined limits; monitoring and corrective action; and documentation kept onsite. For cooling towers, CDC's measures include the lowest practical water temperature, automated chemistry with a measurable oxidising residual, and cleaning and disinfection at least annually.
Requirements are not uniform nationally. Some states and localities have mandatory programmes — Michigan for health facilities, New York for buildings with cooling towers — and others have none, so there is no national requirement to cite. The practical position is simpler than the regulatory one: a building with a cooling tower, a spa, a fountain or a recirculating hot water system, which describes most residential towers, falls within the scope of ASHRAE 188 and should have a documented water management program whether or not the locality requires one.
What a unit owner controls, and what they do not
In a two-pipe hydronic building the owner controls almost nothing that matters. You control fan speed and the thermostat at your terminal unit, and nothing else. You do not control whether the building is in heating or cooling mode, the supply water temperature, whether the plant is running at all, or whether it can meet the load. In a four-pipe building you control mode and setpoint at the terminal. In a water-source heat pump building you control your own heat pump independently and year-round, while the association controls loop temperature and availability.
In every architecture the owner controls the setpoint chosen; the filter in the terminal unit, and whether it is ever changed, which is the leading cause of fan coil underperformance; and keeping the terminal unit and its condensate pan accessible and clear. The owner never controls the plant, the distribution, the loop, the tower, the boiler, or the corridor pressurisation governing how air and odour move between units.
Who owns the equipment in your unit
The general framework, which the declaration and state statute control — and here it varies more than anywhere else in condominium practice. Central plant equipment, risers and mains are common elements; branch piping into a unit is variable. In-unit terminal equipment — fan coils, water-source heat pumps, air handlers, PTACs — is the most variable item in the entire responsibility framework. All four of these patterns are in wide use: the unit is the owner's entirely; it is a common element the association maintains and replaces as part of the building system; the association maintains it but the owner pays for repair and replacement; or the association handles the water side and the owner the air side. This must be read in the specific declaration; a buyer who assumes will eventually be wrong.
Cost, reserves and what it means for a loan
Reserves. Central HVAC is one of the largest reserve categories in a building that has it, and it decomposes into components with different lives: chiller, boilers, cooling tower, pumps, piping and controls. A reserve study with a single "HVAC" line is under-specified, and the distinctive risk is regulatory forcing — refrigerant phasedown, and building performance ordinances in a growing number of cities, either of which can compel replacement of functioning equipment on a schedule the association did not set.
Special assessments. Central plant replacement is a large, lumpy capital event, and because the plant is invisible and its failure sudden, it is a common cause of emergency assessments. One question is worth asking and rarely disclosed: whether the building has redundancy, meaning more than one boiler or chiller so it can limp rather than stop. A Legionella outbreak traced to the building's water is also a catastrophic liability event, and the presence or absence of a documented program is what gets examined afterwards.
Financing. HVAC is generally not a loan issue, and should not be presented as one. Comfort limitations and an ageing chiller are matters to price, not financing obstacles. HVAC enters project review through two narrow doors: deferred maintenance, and habitability — a building without functioning heat is not habitable, and heat is explicitly within the concerns of current secondary-market project standards. Short of that, this is a category where the honest answer is that most conditions are ordinary.
What to ask for. Whether the building is two-pipe or four-pipe; the age of the chiller and boilers and what refrigerant the chiller uses; whether there is a cooling tower and a documented water management program; who pays when the terminal equipment in a unit fails; and whether the HVAC reserve lines are itemised rather than lumped. Establishing plant condition is mechanical engineering work, and who owns the fan coil is a question for the declaration and, where it is ambiguous, for an attorney.
Common questions
Why can I not get heat in my condo in October?
Because you are almost certainly in a two-pipe building that has not been changed over yet. A two-pipe system has one supply and one return carrying either hot or chilled water at any given time, so the whole building sits in one mode and no individual unit can be in the other. Changeover is a management decision and disruptive to perform, so it happens on a schedule rather than on demand. This is a design characteristic rather than a maintenance failure, and short of replumbing the building to four pipes it cannot be fixed.
Who pays to replace the fan coil in my unit?
It depends on the declaration, and this is the single most variable allocation in condominium practice. Four patterns are all in wide use: the terminal unit is entirely the owner's; it is a common element the association maintains and replaces as part of the building system; the association maintains it but the owner pays for repair and replacement; or the association handles the water side and the owner the air side. Read the declaration before assuming.
Does a condominium need a Legionella water management program?
Whether one is legally required depends on your jurisdiction, and there is no national requirement — some states and localities mandate programmes, such as New York's requirements for buildings with cooling towers, while others have none. What is clear is the scope of the consensus standard: ANSI/ASHRAE Standard 188-2021 applies to multi-unit residential buildings explicitly. A building with a cooling tower, a spa, a fountain or a recirculating hot water system falls within that scope and should have a documented program regardless of local mandate.
What temperature does Legionella grow at?
CDC states the growth range as 77–113°F (25–45°C). That is why hot water storage and recirculation temperatures, cooling tower water and spa temperatures all matter, and why CDC's control framework — sediment and biofilm, temperature, water age and disinfectant residual, summarised as STAR — treats temperature as one of four conditions to manage rather than the only one. Aerosol production is what turns growth into exposure, which is why towers, showers, spas and fountains get the attention.
Will an old boiler or chiller affect my mortgage?
Rarely. Ageing plant is a cost and reserve issue, not an agency test, and there is no threshold for equipment age in project review. The narrow exceptions are unaddressed deferred maintenance and habitability — a building without functioning heat is not habitable, and habitability is explicitly within current secondary-market project standards. What matters more is whether the reserve study itemises the plant components, and whether refrigerant phasedown or a local building performance ordinance may force replacement earlier than equipment life would.
My unit is uncomfortable. Is that the association's problem?
Usually it is a shared problem with a divided remedy. Check what you control first: the filter in your terminal unit, which is the leading cause of fan coil underperformance and is almost always the owner's responsibility, a clear condensate pan, and unblocked supply and return air paths. Beyond that, supply water temperature, plant operation, changeover timing and corridor pressurisation are association matters — and in a two-pipe building the limitation may be the design rather than anything that can be repaired.