BUILDING ENERGY - Fall 2017 - 31

FIGURE 2. CO 2 CONCENTRATIONS VS. TIME FOR (A) 10 HOMES WITH FEWER THAN 3.0 AIR CHANGES PER
HOUR AT 50 PA DEPRESSURIZATION (ACH50), (B) 22 HOMES WITH ACH50 OF 3.0 OR GREATER.

FIGURE 3. CO 2 CONCENTRATIONS VS. TIME FOR (A) 13 HOMES WITH NO VENTILATION OR
VENTILATION ON MANUAL SWITCHES, (B) 3 HOMES WITH AUTOMATIC CONTROLS AND
VENTILATION WITHIN 50 PERCENT OF THE ASHRAE 62.2-2013 WHOLE HOUSE FLOW RATE; HOME
13 HAS BALANCED VENTILATION AND SUPPLY AIR DELIVERY IN THE TESTED BEDROOM.

Surprisingly, there was little apparent correlation
between airtightness of homes and CO2 concentrations
(Figure 2). Comparing homes with heating systems
that mechanically "move" air (e.g. furnaces and cold
climate heat pumps)4 with those that do not (e.g.
boilers with hydronic distribution) yielded similar
results. Data did not show that one system type clearly
resulted in "better" indoor air quality. As expected
there was a tendency for peak CO2 level to be higher
in homes with more people and smaller bedrooms.
However, with doors open - i.e. reduced ability to
"trap" air inside the bedroom as people exhale CO2
during the night - occupant density and bedroom
volume had little effect.
Ventilation system was the one variable that
clearly stood out as having an obvious impact on
air quality. Two homes had balanced ventilation
with heat recovery, considered a "best practice" in
modern building construction. Seven homes had
exhaust-only ventilation with automatic controls;
that is, fan(s) operate throughout the day without a
person switching them on. The rest - 13 homes - had
either no ventilation or ventilation that operated
only on manual switches.
Were they constructed today, none of the 22 homes
would pass the Vermont energy code requirements
for ventilation (which calls for adequate spot
ventilation for bathrooms with baths or showers,
plus whole-house system flow at sufficient rate
with automatic controls).5 However, the difference
between the three homes that came close - those
with automatic controls and within 50 percent of
the ASHRAE 62.2-2013 whole house flow rate - and
the other 19 homes (including home 5, which had a

balanced ventilation system, but without a supply or
exhaust register in the bedroom) is dramatic (Figure 3).
DISCUSSION
While not usually considered immediately
dangerous at 1000-5000 ppm,6 recent studies have
linked CO 2 exposure in this range to reduced cognitive
function7 and sensitive individuals may experience
headaches, fatigue and a sense of air "stuffiness,"
to name a few symptoms. Worse, perhaps, is that
as an indicator of inadequate ventilation, elevated
CO 2 may indicate that if there are sources of VOCs,
particulates, moisture and other pollutants in the
home - many of them potentially more serious than
CO 2 - these may also be present at elevated levels.
While this study involved only 22 homes, results
defy the assertion that ventilation is not a concern
in older, leakier homes - sometimes referred to as
homes that "breathe." While there may be greater
movement of air in these homes, there is not
necessarily control of where fresh air is delivered: a
leaky home doesn't give you fresh air where you want
or need it. By contrast, homes that approach (even
if they don't meet) current ventilation standards
displayed much lower CO2 levels, even if not below
the optimal 1000 ppm threshold. This highlights
the need for adequate ventilation in most, if not all,
homes - not just new, "tight" homes.
To optimize both ventilation effectiveness
and energy efficiency, the approach of balanced
ventilation using a heat recovery or energy recovery
ventilator - installing an HRV or ERV - is advocated
as best practice for new construction and retrofits.
This also has the benefit of including high efficiency
NESEA.ORG * 31


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BUILDING ENERGY - Fall 2017

Table of Contents for the Digital Edition of BUILDING ENERGY - Fall 2017

From the Executive Director: A strategic plan for emerging professionals.
From the Board Chair: Taking flight into new territory.
What is Strategic Electrification? Simply Put, It’s an Energy Transformation: A core pathway to deep carbon reduction.
Better Steam Heat: Generating steam system upgrades in New York City.
Going All the Way:What it will really take to achieve net zero energy in Burlington, VT.
Are You Forging the Weakest Link?: A deeper dive into how the quest for resilience alters the design process.
Air Quality in Your Bedroom: Nighttime Carbon Dioxide Levels in the Bedrooms of 22 Vermont Homes: Can occupants of leaky houses breathe easy in their sleep?
Inclusive Diversity Key to Sustainability: Opinion: Sustainability planning must embrace diversity.
BuildingEnergy Bottom Lines: An interview with Jonathan Orpin.
High Performance Walls: Discover an alternative to traditional insulation methods that can reach superior insulation performance with thinner walls.
SAF®– A Solar Faade to Stay?: A technical overview of the newest attachment systems in the low-energy construction market.
NESEA Green Pages: This premier resource for sustainability professionals in the Northeast and beyond is just a few pages away. To have your business listed in next year’s Green Pages and become a NESEA business member today, visit nesea.org/join.
Index to Advertisers
BUILDING ENERGY - Fall 2017 - Intro
BUILDING ENERGY - Fall 2017 - cover1
BUILDING ENERGY - Fall 2017 - cover2
BUILDING ENERGY - Fall 2017 - 3
BUILDING ENERGY - Fall 2017 - 4
BUILDING ENERGY - Fall 2017 - 5
BUILDING ENERGY - Fall 2017 - From the Executive Director: A strategic plan for emerging professionals.
BUILDING ENERGY - Fall 2017 - 7
BUILDING ENERGY - Fall 2017 - From the Board Chair: Taking flight into new territory.
BUILDING ENERGY - Fall 2017 - 9
BUILDING ENERGY - Fall 2017 - What is Strategic Electrification? Simply Put, It’s an Energy Transformation: A core pathway to deep carbon reduction.
BUILDING ENERGY - Fall 2017 - 11
BUILDING ENERGY - Fall 2017 - 12
BUILDING ENERGY - Fall 2017 - 13
BUILDING ENERGY - Fall 2017 - 14
BUILDING ENERGY - Fall 2017 - 15
BUILDING ENERGY - Fall 2017 - Better Steam Heat: Generating steam system upgrades in New York City.
BUILDING ENERGY - Fall 2017 - 17
BUILDING ENERGY - Fall 2017 - 18
BUILDING ENERGY - Fall 2017 - 19
BUILDING ENERGY - Fall 2017 - INSERT1
BUILDING ENERGY - Fall 2017 - INSERT2
BUILDING ENERGY - Fall 2017 - Going All the Way:What it will really take to achieve net zero energy in Burlington, VT.
BUILDING ENERGY - Fall 2017 - 21
BUILDING ENERGY - Fall 2017 - 22
BUILDING ENERGY - Fall 2017 - 23
BUILDING ENERGY - Fall 2017 - Are You Forging the Weakest Link?: A deeper dive into how the quest for resilience alters the design process.
BUILDING ENERGY - Fall 2017 - 25
BUILDING ENERGY - Fall 2017 - 26
BUILDING ENERGY - Fall 2017 - 27
BUILDING ENERGY - Fall 2017 - 28
BUILDING ENERGY - Fall 2017 - 29
BUILDING ENERGY - Fall 2017 - Air Quality in Your Bedroom: Nighttime Carbon Dioxide Levels in the Bedrooms of 22 Vermont Homes: Can occupants of leaky houses breathe easy in their sleep?
BUILDING ENERGY - Fall 2017 - 31
BUILDING ENERGY - Fall 2017 - 32
BUILDING ENERGY - Fall 2017 - 33
BUILDING ENERGY - Fall 2017 - Inclusive Diversity Key to Sustainability: Opinion: Sustainability planning must embrace diversity.
BUILDING ENERGY - Fall 2017 - 35
BUILDING ENERGY - Fall 2017 - BuildingEnergy Bottom Lines: An interview with Jonathan Orpin.
BUILDING ENERGY - Fall 2017 - 37
BUILDING ENERGY - Fall 2017 - High Performance Walls: Discover an alternative to traditional insulation methods that can reach superior insulation performance with thinner walls.
BUILDING ENERGY - Fall 2017 - 39
BUILDING ENERGY - Fall 2017 - 40
BUILDING ENERGY - Fall 2017 - 41
BUILDING ENERGY - Fall 2017 - SAF®– A Solar Faade to Stay?: A technical overview of the newest attachment systems in the low-energy construction market.
BUILDING ENERGY - Fall 2017 - 43
BUILDING ENERGY - Fall 2017 - 44
BUILDING ENERGY - Fall 2017 - 45
BUILDING ENERGY - Fall 2017 - 46
BUILDING ENERGY - Fall 2017 - 47
BUILDING ENERGY - Fall 2017 - NESEA Green Pages: This premier resource for sustainability professionals in the Northeast and beyond is just a few pages away. To have your business listed in next year’s Green Pages and become a NESEA business member today, visit nesea.org/join.
BUILDING ENERGY - Fall 2017 - 49
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BUILDING ENERGY - Fall 2017 - 76
BUILDING ENERGY - Fall 2017 - Index to Advertisers
BUILDING ENERGY - Fall 2017 - 78
BUILDING ENERGY - Fall 2017 - cover3
BUILDING ENERGY - Fall 2017 - cover4
BUILDING ENERGY - Fall 2017 - outsert1
BUILDING ENERGY - Fall 2017 - outsert2
BUILDING ENERGY - Fall 2017 - outsert3
BUILDING ENERGY - Fall 2017 - outsert4
BUILDING ENERGY - Fall 2017 - outsert5
BUILDING ENERGY - Fall 2017 - outsert6
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