I had a very nice chat with a client the other day.
He and his wife have dealt with a "too hot upper story" (in their 1970s split-level) for 20 years.
They have sufficient attic insulation (about 12-14"), a partial air barrier at the attic floor, and ducts in the attic wrapped to R-4 (but not sealed).
They know their options for improving comfort in the summer (i.e. seal the ducts, boost the insulation level of the ducts, install a radiant barrier, achieve better attic ventilation).
Our conversation has led me to question some assumptions I have formed over the past few years.
I am hoping that y'all can weigh in (as objectively as possible) on the following remedies (keeping in mind that improving the level of attic ventilation, at ridge and soffits, is implied):
1. Remove the existing duct wrap insulation. Seal the ducts with mastic, re-wrap the ducts in FSK foil-faced duct wrap, and blow cellulose on top of the ducts.
2. Aeroseal the ducts throughout the house ONLY.
3. Install a high-quality radiant barrier in the attic.
Cost may not be a deal-breaker, but a solution will HAVE to be provided for the expense.
Thanks in advance!
When I am asked to fix this home. I start with a Heat Loss and gain, blower door IR sq ft, then I find the CFM per room then I find the CFM per room and comprare the supply and return to ACCA MJ room to room, or leval/zone. Most of time there is no return to top floor and very little supply - most home have most return in basement. I cheack the Static Presser both return and supply 90% of time its much higher than listed on air handler. I give 6 options to fix the house and talk about it
The most bang for your buck will come from airsealing the attic plane and sealing the ducts.
Adding insulation on top of ducts after sealing (#1) will help more than changing shingle colors. If the roof does need replacing, there are many non-white shingles that are "reflective" available.
An alternative to explore re the windows would be interior storms. Check http://www.indowwindows.com/ About 20% of the cost of replacing with high quality replacement window. Invisible from outside - important in historic districts restrictive HOA etc. Will double R-value of single pane (to R2- wow) as well as reduce noise and stop condensation. Important that they seal well to be effective. Consider experimenting with a couple in a south facing room to see if helps your situation. The function of a storm window is to protect wooden windows. In my experience, exterior storms do nothing for exterior asthetics and little for efficiency or as they are vented to get rid of condensation.
Disclosure- I just picked up a dealership for these.-in Maine. After some research, I chose these because I work in many beautiful old homes(125 years+) with homeowners that do not not want to lose the character of the exisitng window and wavy glass and as we all know, windows are not high on the payback scale.
Insulation beyond code (an extra R10 over code is cheap) airsealing and proper attic ventilation will do much more for your client than a radiant barrier and contribute to comfort and lower energy bills year round.
We have successfully treated this same problem in perhaps 1000 of this same house in the Baltimore/Philly area over the last 4 decades.
The split-level is the second worst energy problem we see behind the Cape Cod syndrome. The split wall is usually open down to the lowest level, which may be a basement or a crawlspace. I will sometimes toss a nickel down one of the wall cavities in the lower of the 2 attics with the HO watching, then go to the basement and pick it up off the floor. Huge hole up the center of the house and the source of perhaps 5-800 CFM50 of that rather large leakage rate you measured.
The split wall is where the action is in this house. You need to horizontally seal the studs as they go down lower than the attic floor. There is frequently a kitchen cabinet soffit right against that wall, and this complicates matters. A fossil fuel chimney may also go up that wall, giving you several poor choices for what to put in the envelope and what to leave out of it. Also, low roof pitch can make all of this unpleasant. Then seal the upper and lower attic floors in the normal fashion.
Dress up and add insulation to the exposed part of the split wall, along with the angled area over the stairs. Then add 1/2" or 1" of rigid foam board to that wall.
Get all of the attic ducts down onto the attic floor - cut straps, re-route through trusses if it has them - then seal them and blow over them - 4-5" on top tapering to the side should do it. Shouldn't need more insulation in general, but if you have had to spoil it by working in it, you may want to add 3" to even it up.
Many of these houses have a single car garage under the taller section where the bedrooms are. You will have to dense pack the ceiling of that garage to keep air out of the house proper and get insulation to touch the flooring above. Sometimes the duct soffit hangs down in that garage ceiling - you will have to be creative with the dense pack hose.
These houses were built before A/C was standard, and before the A/C duct system needs were fully understood (are they understood yet?). So the house probably heats OK, but the larger flows delivered by the A/C mode won't fit, and the second floor ducts are probably the hold-up.
So now for one of the most important items - do a flow check on the registers, preferably with a flow hood of some sort. You don't need a Manual J - there are so many millions of these houses that the HVAC guys now better than to put in a too-small unit. Just make a judgement about the amount of air you are seeing and work the dampers (if it has them) to distribute the total in a more equitable way. (use 400 CFM per ton as a starting point, and 80 square inches of supply and return trunk per ton as a starting point) You will have to train the HO on how to change dampers for winter/summer to favor the appropriate level. To check for adequate return, with the stat in cooling mode (higher fan speed) use your flow hood to measure a register. Then remove the side of the air handler cabinet and push the safety switch to get the blower to run. You should see no more than a 5-10% increase in flow at the flow hood. More than that (I have seen 50%+) means the total return is inadequate.
And you don't need return on the top floor, just adequate return somewhere in the house that all registers can get too - undercut doors, install transfer grills, use your pressure gauge - but once you are outside of each closable door, you only need one return somewhere in the house to be effective.
Do your research on radiant barriers and you will never recommend them again in the DC area. Anything over R-19 and they are not cost effective, and if you have R-19, it will save more energy cheaper to just blow more material. Remember it is all about the temperature of the drywall ceiling inside the house. What is the cheapest way to get the lowest (in summer) surface temperature - turns out to be about R-38 or a little more.
Same for attic vents - if you have properly sealed the attic floor (and the split wall which is nothing more than the attic floor turned on its side) no moisture will end up there, and with all that insulation, attic heat won't matter.
Same for windows, unless they are the single pane aluminum sliders so common on the back and sides of these houses - even with stroms we recommend changing them to keep the window sills from rotting.
Do it now before the attic gets too hot!!
You note overheating on the south side (naturally.) Assuming the typical roof overhang of maybe 12 inches I would add some type of shading device, properly dimensioned to work effectively to keep the solar gain down. And I'm a big believer in "insulating the glass" with a better-quality insulated shade. And the new shades can be the "pretty piece" they can show the neighbors. I did a similar home, 1952 vintage and original, recently; ended up with a TON of improvements recommended. One interesting one was to convert the garage to living space, since it's already being heated & cooled by all the leakage, and it's too small for their vehicles.