There is nothing like setting a dramatic target to get people's attention, and the Urban Green Council is certainly doing so, with their proposal to reduced New York City's CO2 emissions by 90% by 2050. What's more, they propose doing it by renovating and rehabilitating existing buildings with a series of measures that are achievable with today's technology, no silver bullets required.
Some of the ideas they propose are absolute no-brainers and should be part of the building code right now; I am not sure about some of the others, and whether they have thought through all of the implications of scaling things up to New York City sizes. It's HUGE: we are talking about replacing 99 million windows, 5.7 billion square feet of insulation, 5.65 million residential units and 86,000 commercial buildings. Here's the plan:
Lower vision glass to 50% maximum
This is a serious no-brainer; there is no need for floor-to-ceiling glass, and it is actually uncomfortable in both summer and winter. Architects and builders like it because it is easy one-stop shopping, but it should just not be allowed. (See Allison Bailes' great article A good window is still a poor wall)
Increase insulation on solid walls
They are looking for an average of R-20, which isn't a huge stretch. Prepare for New York to turn into Stucco City, as they suggest that the exterior surface is preferable for insulating.
Owners of brownstone town houses and many other buildings with decorative facades will not want to utilize external insulation, but other options exist, starting with additional interior insulation. Interior insulation must be evaluated carefully, as not all masonry can withstand the increased temperature cycling that will occur if it is isolated from the interior.
There is no mention about the serious concerns some people have with the use of plastic foam insulation, which I have covered in Polystyrene Insulation Doesn't Belong in Green Building and Why Plastic Foam Insulation Is Like a Twinkie: Lessons Green Builders Can Learn From Michael Pollan
Incorporate triple glazing
Here again they are realistic and reasonable, suggesting that it can be done either through window replacement or by adding another layer of glass.
Add sunshades to south windows
I cannot imagine that this would do much at all, given how much shade there is in New York from other buildings. But I do love nice shades.
The interaction of architectural measures
Here, they demonstrate a real understanding of the complexities of green building.
The levels of change we are examining in our models will raise eyebrows. Each of the proposed measures above calls for a level of insulation, air sealing, or glazing that is not currently regarded as worthwhile. If the measures were regarded in isolation in a typical contemporary building, there is truth to that. There is no point in adding insulation up to the R-20 level (over R-10) if heating and cooling loads driven by infiltration, ventilation, and equipment inefficiency are left at their current high levels. The last R-10 increment of insulation will do very little to the overall heating or cooling load, since the heat will be leaving or entering the building through those other modes.
However, the only path to a truly low-energy building is to reduce all loss pathways. When this is done, and all routes for unwanted heat loss or gain are treated as a unified whole, then each of the measures considered here will still make significant contributions to energy use reduction, even at these “extreme” levels.
Indeed, if the buildings are sealed so tightly, there are going to be all kinds of secondary problems such as moisture buildup and mold, so heat recovery ventilators are going to be needed in every unit.
Heat pumps: Mini-splits and ground source
Here, the key proposal is to get off the central coal-fired central steam heating system and go to electric-based heat pumps. I wonder if this is a good idea.
Once buildings are insulated to R-20 and have triple-glazed windows, it isn't going to take much to heat and cool them. Mini-split heat pumps are proposed for residential units; these are essentially air conditioners that run backwards in winter, sucking heat out out of the air and moving it to the interior. That is a serious number of condenser units sitting outside sucking a few calories of heat out of the winter air; I wonder if it could actually have an effect of changing the micro-climate, making New York warmer in summer and cooler in winter.
The idea of drilling the number of wells needed for a ground source system for all the larger buildings is beyond comprehension. Where would you put them all? Tom Rand's little Planet Traveler Hotel in Toronto took eight wells 350 feet deep.
And if you are in a City surrounded by rivers and oceans, why would you bother? Why not just do a deepwater system and let the Hudson River do the work?
Green buildings should be healthy buildings
There are other issues. Currently a lot of air is pumped into corridors to pressurize them; this ensures that smells from cigarettes and cooking don't migrate out from the units and annoy neighbors. It also controls smoke in case of fire. Fresh air comes in around the entrance door and leaks out the windows or the bathroom exhaust. Under this proposal, New York apartments will manage their moisture and smells with 5.65 million heat recovery ventilators. Simple, central, leaky systems are replaced with individual and complicated heat pumps and HRVs, all of which need maintenance and filter changes. I worry that it is all just too complex a system.
There are serious health implications if these systems don't work, if moisture builds up and mould starts growing. All of these foam insulations and caulks are full of flame retardants and VOCs and other chemicals that can build up if there isn't proper ventilation. In a lot of ways, leaky buildings are healthier buildings because of the high rate of air change.
On the other hand, it is a bold, aggressive proposal that would create tens of thousands of jobs, would probably pay for itself in energy savings if they actually achieve the "unified whole", and would make New York a much greener, if much uglier, city of vinyl and stucco.
Fascinating reading from Urban Green.