CNC Report 08.26.24 8.5x11 - Flipbook - Page 26
MAKE ENHANCEMENTS TO THE ENVELOPE
Since the envelope is a passive system, how can it be improved before active systems are upgraded?
What passive systems (i.e. thermal envelope, WWR, overhangs, access to daylight, etc.) can be
improved most effectively based on existing structure and intended new use?
1. Window-to-Wall Ratio and Glazing Comparisons
The window-to-wall ratio (WWR) is crucial in embodied and operational carbon considerations. A lower
WWR translates into reduced façade embodied carbon and lower energy requirements for heating
(operational carbon) due to decreased window surface area, which is prone to heat loss.
In regions where cooling is more necessary than heating, the window-to-wall ratio (WWR) remains
important for operational carbon considerations. Still, in these cases, it is crucial to consider solar
control to avoid high solar gains.
For example, the chart on the left illustrates the total carbon footprint over the lifespan of a typical sixstory mixed-use residential building (MURB) with a 40% WWR:
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Initially, the carbon footprint stands at 4.2 million kilograms of CO2 equivalents (KgCO2eq).
A reduction of 10% in the WWR results in a decrease of 9,660 KgCO2eq in carbon footprint.
Conversely, increasing the WWR by 5% adds 11,771 KgCO2eq to the carbon footprint.
While alterations in the window-to-wall ratio do impact the overall carbon footprint, it is evident that
these decisions have a more pronounced effect on ongoing energy consumption.
2. Insulation
The embodied carbon footprint of envelope assemblies is influenced by the quantity of insulation used
and the specific materials chosen. The chart shows how much carbon different insulation materials
use to reach a certain level of insulation. Utilizing natural materials for insulation, such as biomaterials,
could aid in carbon storage although it requires thicker walls. In contrast, synthetic insulation requires
less space but has significantly higher embodied carbon emissions due to its manufacturing process.
3. Triple vs. Double Glazing
Triple-pane insulating glass has about 1.5 times the embodied carbon compared to dual-pane glass,
primarily due to adding a third glass pane. This higher embodied carbon footprint needs to be
weighed against the lower operational carbon footprint to assess its overall impact.
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