Climate Control Challenges

The Building Committee has received several questions about the high temperatures within Andover High School resulting from this week’s weather. Below we are pasting information from a prior AHS Facilities FAQ that summarizes facility conditions identified in 2018 which make HVAC upgrades challenging and expensive.


Q3. Why is the temperature within Andover High often uncomfortable in winter and summer? What are the major contributing factors?

A3. The climate control systems in Andover High are well maintained and actively managed, even earning Energy Star rating for the efficiency of current systems. However, these current systems rely on old technology and major components — including boilers and unit ventilators — that are reaching the end of useful life and need replacement.

HVAC experts have observed that meaningful replacement of Andover High’s aging climate control technology would best be supported by also upgrading other critical energy components.

For example, almost all high school windows are drafty and do not sufficiently block UV light, allowing heat loss in the winter and heat gain in the summer. Unit ventilators are the large boxes typically seen under windows along exterior walls to heat outside air as it enters classrooms during cold weather. The technology they use has been largely unchanged in over 60 years.

But most notably, the current building is constructed of concrete with no insulation in the original exterior walls and with floors that create a “thermal bridge” by extending past the building façade, thereby drawing heat out of the building in the winter and increasing room temperatures in the warmer months.

Replacing the extensive unit ventilator system without also addressing the building envelope of the original building would provide only very limited climate improvement.*

Additionally, in each classroom, unit ventilators bring outside air into the building to reduce carbon dioxide (CO2) levels. When rooms are overcrowded, CO2 increases faster than heating elements can keep up with the airflow, resulting in cold outside air being blown into classrooms throughout the winter. The unit ventilators are also loud and distract from learning.

A facility project that simply replaces unit ventilators in-kind — rather than upgrading the heating technology and improving the building envelope — will bring a continuation of the same climate control problems, and may not even save money in the long run. In addition to solving these problems, a modern climate system would bring an opportunity for replacing the unit ventilation system with a displacement air system similar to the system installed at Bancroft Elementary. This would increase comfort during shoulder seasons and allow year-round use of the building.


Taken from:…/9109/AHS-Facilities-FAQ–2018-09-13V2

* Addressing just the building envelope (not including any mechanical system upgrades) was estimated to cost more than $40 million in 2018, and construction costs have escalated since that time.