"Americans can always be counted on to do the right thing...after they have exhausted all other possibilities." Winston Churchill
How much does it cost to perform a deep-energy retrofit at a 100-year-old single-family home? Thanks to a recent study in Utica, New York, we now know the answer: about $100,000. http://www.greenbuildingadvisor.com/blogs/dept/musings/high-cost-de...
The energy retrofit work greatly reduced the air leakage rate at all four buildings; final results ranged from 2.2 to 5.0 ach50. The homes had impressive levels of energy reduction; however, the energy-reduction goal of 75% was not met. Overall energy use (including space heating, domestic hot water, and electricity) was reduced by 60% to 65%. Electricity use in the four buildings actually went up. (Among the new appliances that added to the electricity load were the homes’ mechanical ventilation systems.)
The average cost for the work was $112,000 per building, or $89,783 per housing unit. The average annual energy savings was 393 therms of natural gas (11,486 kWh) per housing unit. Since the cost of natural gas in Utica is $1.65 per therm, the average annual energy savings are $647 per housing unit.
In other words, the simple payback period for these retrofits was 139 years.
The existing forced-air furnaces in these buildings were all removed, and new hydro-air heating systems were installed.
Unfortunately, it is unclear what percentage of energy use savings.is attributed HVAC imrovement.
Below are results of another super-insulation retrofit: "Teaching old houses new tricks, Build Boston 2010, November 18, 2010"http://www.buildboston.com/ResPlus/Images/Document/BuildBoston_B56.pdf
Furthermore, a concerns are raised today about insulation materials impact on environment. A study published by a team of researchers in Building Research & Information makes it clear that the very materials that provide us with such energy efficiency are pumped full of harmful flame retardant chemicals.
The reasonable questions follows from above results:
Heating system upgrade is a low hanging fruit often neglected when insentives are easily available.
A good example: 179 Henry Street. A Case Study in Converting from Two-Pipe Steam to Hydronic Heating (http://www.1energygroup.com/index.php/newsroom-3/234-179-henry-stre...)
The cost of the heating work was $610,774. For the 18 months prior to weatherization, the building used 9,580 MMBtu of #6 fuel oil per year at a cost of $137,450. A year and half later, the building has used 3,294 MMBtu of natural gas at a cost of $45,776, a 33% savings.
.payback period for this retrofits (610,774 /(137,450 - 45.776))*1.5 =~ 10 years
It's a bigger project then insulation retrofit projects above, but ROI comparison is valid, because ROI values are relative (years).
Actually, obsolete heating system conversion into hydronic is not the best available solution.
Hundred years ago steam system conversion into vacuum Paul system on average saved 35% of fuel cost and paid back within one year ("The Lost Art of Steam Heating" Dan Holohan). As it said, laws of physic did not change in last hundred years and this inexpensive and very efficient solution to steam system retrofit is readily available today.
Steam system conversion into vacuum was successfully utilized by ITC in 2006 Peter Cooper Village project (http://www.green-buildings.com/certs/ITCSteamSystem.pdf) Tests of efficiency were conducted by on-site facility management utilizing Con Edison meters in two five-building clusters with similar exposures. The tests resulted in a 27% reduction in steam consumption from the steam system baseline, resulting in approximately a 5 year payback for the $28,500,000 investment.
With progress in modern plumbing, materials and controls it's possible to get more benefits from vacuum heating. Basic info about modern Vapor Vacuum Heating (VVH) concept, cost analysis, etc. can be found in article for ASHRAE/CIBSE symposium London 2012 http://www.cibse.org/content/cibsesymposium2012/Paper106.pdf.
Research demonstrated that it is possible to integrate VVH with condensing boiler as well.
Compared to conversion into hydronic, steam system retrofit into Vapor Vacuum Heating is from 30-40% less expensive (up to 70% if existing boiler is salvaged), so pay back period can be dropped even more - to 3-5 years..