Load calcs and action plan
We have just received our initial load calcs, as we plan to upgrade HVAC from oil to high efficiency heat pump. We are in CZ4.
1. Our laundry room is poorly insulated and requires well over 6k BTU to heat. The room is adjacent to garage and separated from kitchen via louvered door, with one HVAC supply duct. Properly insulating this room would cost thousands of dollars. Can we simply buy an attractive, airtight door to replaced the louvered door and then treat this room as “semi-conditioned” space? We would leave the supply duct as is and just plan on this room being a bit cooler that the rest of the house in the winter (but less of an expensive heat-suck).
2. Our basement is poorly insulated, with a finished rec room and two crawlspaces. Counting two crawlspaces, the basement requires 20k btu to heat. This seems very high! Should we include the crawl spaces in the btu calculations? How else do people reduce the heating load in poorly insulated basements?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Frank,
There are several issues here.
The first issue is whether you have obtained an accurate load calculation. I suspect that you haven't. In Climate Zone 4, it would be very unusual for a basement to have a design heat load of 20,000 BTU/h.
For more information on load calculations, see "Who Can Perform My Load Calculations?"
(Note, by the way, that the units for heating loads is BTU/h, not BTU.)
Q. "Can we simply buy an attractive, airtight door to replaced the louvered door [to the laundry room] and then treat this room as 'semi-conditioned' space?"
A. You can try that approach if you want. But if you leave a forced-air supply register in the room, blowing hot air from the furnace into the room whenever the furnace comes on, it isn't clear that a solid door would reduce your energy bills. You might find that the laundry room is now hotter, not cooler, that it was with the louvered door.
Q. "How do people reduce the heating load in poorly insulated basements?"
A. There are two steps you need to take: air sealing work and insulation work. Read these two articles:
"Air-Sealing a Basement"
"How to Insulate a Basement Wall"
Thank you Martin. The calculations were performed by a ResNet rater. But, we understand there is debate, which is why I posted.
Should closed crawl spaces be included in basement heat load calculations?
Would replacing the laundry door reduce our heating load? (Motivation is avoid the 6k btu/h - we're not particularly concerned with temp of laundry room itself).
Frank,
Q. "Should closed crawl spaces be included in basement heat load calculations?"
A. Insulated sealed crawl spaces don't need to be conditioned and shouldn't be included when calculating a home's design heating load.
Q. "Would replacing the laundry door reduce our heating load?"
A. As I already noted, if you don't disable the supply air register in the laundry room, replacing the existing louvered door with a new solid door could either (a) make the laundry room hotter (increasing the heating load) or (b) make the laundry room cooler (decreasing the heating load), depending on the airflow coming through the register.
If you want to decrease your heating load, you should cap the duct to the laundry room and replace the door with a solid door. Note, however, that this move will change the air flow to remaining registers, so you need to know what you're doing (and you need to maintain minimum required airflows through your furnace). Note as well that you don't want to freeze plumbing pipes in your laundry room during cold snaps.
Is it an un-insulated walk-out basement with most of the wall area above-grade? 20KBTU/hr is pretty high for a basement in zone 4 if it's mostly below grade, but not unheard of. A room load of 6KBTU/hr is also pretty high.
A load that high doesn't drop to zero when you don't actively heat it to 68F. Even when left to idle at 50-55F or whatever it's likely to still represent a large fraction of the house's total heat load. Air sealing & insulating the basement and crawlspace walls would have an impact on both first-floor comfort and energy use, and even an unheated basement would likely never drop below 60F even in the dead of winter.
Have you run a fuel use heat load calc to sanity-check the Manual-J yet? See:
https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/out-old-new