Living attic vs larger footprint: where to build in extra space
Design considerations for Pretty Good House in zone 6a.
If one lurks on GBA for long enough, they might be led to think:
1) Basements are traditional but arguably not the most cost effective solution to build a PGH. They are a hole in the ground with the requisite water issues, use a lot of concrete, and cost a lot.
2) A traditional ‘cold attic’ (insulating at the ceiling place) is more cost effective—and arguably more robust and resilient—than insulating at the roofline. All other things equal.
All well and good. But when it comes time to talk someone into adopting both of these approaches, they might wonder where they are going to put all their ‘extra stuff’.
Sure, one can make the main floors larger in footprint, but then you’ve built a larger house just for ‘extra-space’ rather than utilized ‘bonus’ space inherent with attics and basements.
To be more specific: If the primary goal is to forgo a basement for the aforementioned reasons, might it be sensible to consider insulating the roof-line to gain the bonus 1/2 story under the roof? Consider that the structure is wide enough (28′-32′) and the roof pitch steep enough (10/12) that the ‘bonus’ attic space would be quite large and livable).
Possible benefits to insulating the roofline for the added 1/2 story:
· The overall size of structure remains the same. This intuitively feels more resource efficient. You are taking advantage of space already existing—you’re just moving the location of the thermal control layer.
· You will never add that much square footage of living space as cost effectively (I imagine). With 2 main full-stories, you would be gaining roughly 25% additional living space, and a full 50% more space when storage is included (attic triangles).
Benefits to increasing footprint instead:
· Insulating the ceiling plane is more cost effective, apples to apples. (until what point, given an increasing footprint size?)
· If you’re OK with NOT increasing Sq. footage to the same extent as the bonus 1/2 story would, perhaps this is actually the more frugal approach?
What is a wise design mantra to approach this desire for ‘extra space.’?
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