Philadelphia Medicine Spring 2020 - 30

p h i l a m e d s o c .org

FEATURE

ENERGIZING OUR
FUTURE BUILDINGS
By: Walter Tsou, MD, MPH

mericans spend about 80% of our hours indoors in buildings.
Most are heated with some type of fossil fuel, generating
an estimated 560 million tons of CO2 or one-tenth of US
emissions. What if we could live indoors and heat and cool our
homes without generating so much fossil fuel which we know is
a major contributor to climate change? The type of radical shift
needed to reach our climate change goals would require a 75%
reduction of CO2 production by our buildings. This presents a
huge challenge. Can we live in our homes or offices and not burn
fossil fuels at all?

Philadelphia, like most East Coast cities, has an old housing
stock built at a time when we really did not understand much
about insulation, weatherproofing, and ventilation. I live in such
a home in Mount Airy which has almost no insulation, but its
stone construction manages to keep most of the elements out of
the house. Back in the 1930s when my house was built you closed
the windows and lit a fire in the fireplace during the winter and
opened the windows in the summer and that represented our best
understanding of heating and cooling. The house was heated using
hot water radiators and an oil burner in the basement. No ducts
were installed that could be used for ventilation or air conditioning.
Summers were never that hot that a few ceiling fans could not
handle. Probably most of the homes in Philadelphia are like this

and air-sealed coupled with balanced energy recovery ventilation
for a comfortable, healthy and durable science-based design that
is near-zero energy. Thus a smaller solar PV array can be added to
reach zero or plus energy use.
It is currently a voluntary standard for energy efficiency in
the USA although in Europe it is the current standard in many
countries or will be in others in the next few years. Passive House
standard is not confined to residential homes. It has been used in
office buildings, hospitals, factories, and schools. A small number
of certified Passive House architects are in Philadelphia and you
can probably count the number of Passive buildings on your hands,
mostly private homes or affordable multi-family senior residences,
but this may be changing.

The greatest public health threat worldwide and potentially in
Philadelphia is climate change. Already we have set new records
for rainfall, for prolonged hot days over 90°, and for threats associated with sea-level rise. Philadelphia gets its water from our two
great rivers, the Schuylkill and Delaware. The confluence of those
two rivers is near our airport in South Philadelphia. In months of
prolonged drought, we have already seen saltwater infiltration go up
the Delaware River, threatening our water supply. (Fortunately, we
have developed reservoirs upstream in anticipation.) Nevertheless,
as sea levels rise, tidal flooding could begin around the airport, parts
More modern homes are now built with wood framing, in- of South Philadelphia, and along the river banks. Think trying to
terspersed with a Tyvek exterior lining, fiberglass insulation, and reduce our emissions is difficult? Try rebuilding our airport, South
then a drywall interior. Despite these technological advances in Philadelphia and our water supply.
how we build homes, the seams are frequently inadequate and still
Philadelphia's major energy source for heating our buildings
represent areas of the air leakage and cold infiltration as confirmed is natural gas. Natural gas is considered plentiful in Pennsylvania
by a thermal survey.
because our state has fully embraced fracking over the Marcellus
The new advancement of homes is based on a rigorous German Shale. However, natural gas is not only a fossil fuel but its main
energy standard called Passiv Haus Standard, that advanced and ingredient, methane, is a very potent greenhouse gas which over a
codified research on super-insulated buildings done in North Amer- 20-year span of time is 86 times more heat-trapping than carbon
ica in the 1970s into an energy modeling platform with practical dioxide. Because of this, our ability to reduce and even eliminate
construction practices. Passive House Standard as it is known in burning natural gas has to be one of the key solutions to reducing
the USA. It is not passive solar, but rather the Passive refers to a greenhouse gas emissions worldwide. To add to the complexity,
climate-specific enhanced building envelope that is super-insulated Philadelphia is the owner of Philadelphia Gas Works (PGW).

30 Philadelphia Medicine : Spring 2020

https://philamedsoc.org/

Philadelphia Medicine Spring 2020

Table of Contents for the Digital Edition of Philadelphia Medicine Spring 2020