Exposed ductwork?
mikeolder
| Posted in General Questions on
I want to build on stem walls with a slab floor. I’m aware trusses with duct chases can be built, but they have their air sealing issues and don’t address the branch ducts which need to supply conditioned air over windows. Why not build 1′ taller and hang spiral or oval ductwork? This would also make additions, or in my case, enlarging a one bedroom into a three bedroom via an oversized garage possible for a new owner.
Thanks
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I'm always for taller ceilings. I would not even drop the whole ceiling as in most cases you only need a small interior bulkhead for the duct.
You can also look at running ducts inside walls. You can run for example say a 6x18 trunk on edge on top of a 2x4 interior non load bearing wall with just a small jog for the extra width. With some pre-planning, can also be buried behind built ins like above kitchen cabinets or built in storage. This way you only have the bulkheads in a couple of places, the rest of the house you can enjoy the taller ceiling.
Not a fan of exposed duct except for loft style places. Plus they collect dust on top.
Akos said.. "I'm always for taller ceilings. I would not even drop the whole ceiling as in most cases you only need a small interior bulkhead for the duct."
Thank you.
So you install the furnace and duct, build the bulkhead around the duct, and then fasten the interior non bearing wall top plate to the bulkhead? Then undercut interior doors to pull return air to one cental grill at the furnace closet? I always had the luxury of a basement to run my duct and panned joist spaced for returns, so this is hard to visualize. It also sounds like the supply registers are at the non bearing wall, not over the windows.
Maybe I should design with a basement, because we see tornado's in Iowa, and it would make installing mechanicals straight forward. And design a two bedroom, with room for a third in the oversized garage.
Basement is a regional thing. If you are in an area where basements are the norm and people expect to see one, I would not build without it.
For a slab, I think I would build close to my post #24 here except with proper stem walls.
https://www.greenbuildingadvisor.com/question/poking-holes-in-a-double-wall-wood-on-gravel-frost-protected-shallow-foundation-assembly-in-4a
You use a downflow air handler and run all your services through the floor if you use 2x6 or 2x8 joists. Bonus, you now have wood flooring which is much easier on the joints.
As for running interior ducts, my suggestion inside an interior wall is one a way to hide the duct, there are many other ways that might be simpler. For example running a bulkhead on the inside of bedrooms above the door is pretty much not noticeable as well as they are outside the living space.
If you post a sketch of your floor plan, we can see where you can hide ducts. With higher efficiency structure with better windows, you don't have to have registers bellow windows (still the best spot though).
Most homes in my area have basements, so I'm redrawing my plan at 28 feet wide instead of 38. I've never actually completed a floor plan yet as I was more focused on a simple shape and roof. The closest I ever got was on a two story. I need 14' of height for a car lift in the garage and was back and forth, but decided to use 38' scissor trusses instead of a two story. I'm on a hilltop but don't have enough elevation change to have a walkout so the basement probably won't be utilized to its potential because of the large garage size. Below is a sketch of my first design, where someone could remove the lift and add another couple of bedrooms, but I ditched the idea. I didn't like the roof/wall intersection, and the garage was too small. The second sketch has some big headers. Where can I get ideas for functional floor plans? Thanks Akos
Mike,
I would figure out a floor plan and house layout that works from you and work from there. Equipment and ducting can always be made to fit, no need to design the house around it.
If you have the land, I would go for a detached garage maybe with a breezeway connecting it to the house. This way you are dealing with two separate structures and each can be designed to serve its purpose the best.
You mentioned a detached garage because "each can be designed to serve its purpose the best" I planned on 6" Bonfiglioli walls and R60 ceilings in both, thinking even without heating , the garage wouldn't freeze using a Un-insulated slab. Un-insulated would also keep the garage cooler in the summer if I kept the doors closed like a shop I used to work in. Perimeter insulation over the stem wall would perform well, but protecting it from the mower and weed trimmers is nearly impossible, so that's the weak link and I will keep it as low as possible..
I'm concerned about resale value, so would a detached be more sell able? Another aspect is the mobile home I'm living in sits on the only spot a walk out could work, and work very well considering the mile long view. I'm thinking maybe do the detached, and instead of investing more money in the mobile home, sell it and invest that money into a 2 bedroom home that actually builds equity.
Because most people would think it was strange and ugly and give the room a commercial feel.
All of that would make it hard to resell the home when it comes to sell.
Walta
Thanks Walta.
You should see the stack of scale drawing I've compiled over the years, but now I need to make a decision. I imagine you have a program where you can modify designs more easily.
I'm no fan of basements. They are expensive and prone to mold and mildew. Why start building a house by digging a moldy pit to put it on? (Yes, it can be built dry and that's were it starts to get expensive.)
That said, there may be reasons, and a tornado shelter is one of the few good ones. Still, though, with a bit of planning a tornado room built of concrete block can be worked into most house plans and it's cheaper to build above grade than below. The room can serve as a pantry or storage for normal use.
Another possibility is a slab on grade, with only a very small basement where needed. That's what Frank Lloyd Wright did in most of his Usonian houses. Check out the Jacobs House plan and note the stair between the kitchen and bath. It leads down to a small basement under those 2 rooms. The rest of the house is built on a slab.
Regarding ductwork - Think of your typical hotel, with a central corridor with bedrooms on each side and each bedroom having a bathroom backing onto that corridor. Typically the corridor ceiling is lower and provides space for the main ductwork, a spine running down the middle of the building, with branches going over each bathroom for exhaust air, and continuing to the bedrooms with vents high up in the wall of the higher ceiling portion for supply air. Some thoughtful planning early in the design phase can accommodate efficient schemes like this.
I think one reason basements get built is that once you need 4 foot frost walls, the incremental cost to build out a basement is not huge. They get wet and moldy due to poor building and water management.
Storage space workshop space and all not usually taxed as usable square footage.
All good reasons.
How about when there's a plumbing leak, or the bathroom needs remodeled?
With a slab, I'd have to rent a quicky saw.
I don't like crawl spaces since I've worked in many. But would it make any sense building the basement with a 6 or 7' ceiling considering I don't have enough fall for a walkout? Probably wouldn't save much though.
That's exactly the thing. Once you have to dig down 4' for a frost wall, and if you have your finished floors a couple of feet above grade, you have a 6' or 7' crawl space. At that point, making it an 8' basement does start to make sense. Yes, insulation, waterproofing and footing drains add a bit to the cost, but it's still the cheapest square footage you will get, especially if there is no need to finish right away. And if basements are expected locally, that's another plus.
I do like shallow frost-protected slabs, but they do have their difficulties with infrastructure and repairs. They save a lot on materials use and cost though. All trade-offs to consider during the design process.
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gusfhb,
I think it depends on your code. Ours mandates enough requirements (insulation, protection of wiring, conditioning) for basements that they have to be built as what are basically finished spaces.
I’m also not sure what makes them cheaper than other conditioned spaces. What except for cladding is missing that makes them less expensive than above grade. living spaces - especially when you have to devote floor area to a stair to access it?
Then you end up with living spaces that are demonstrably less pleasant than those above, while being much more prone to water damage. Unless a good amount of the basement is above grade, I just don’t see much benefit.
Unfinished basements are taxed less in Iowa county. Mine in town looks like a hardware store.
Mike,
What does the Iowa code now require for basements? What insulation, electrical wiring, conditioning, etc?
I'm just a retired HVAC guy Malcolm, but It's not uncommon to see bare concrete basement walls. Then the homeowner does what they want to increase value, but I would never finish a basement even though the site is on a hilltop. I have an appointment with a local engineering consultant and expect she will apply Iowa codes to my drawings to develop a detailed blue print all contractors will sign off on. But I just learned she isn't certified, her husband is. I should have never approached anyone without a print, because I've already burnt one bridge talking about a capillary break over the footing. There are no code inspections in my area which could be troublesome. One builder who built what looks like a very nice house down the gravel road from me said we could work something out on a napkin.
response to #8 - The slab on grade is not the one solution to all the world's problems. Of course it has its drawbacks. Under-slab utilities is the one that bothers me the most.
But the frost protected shallow foundation is now an option, something it wasn't back when the tradition of building basements first appeared in the northeast.
I would opt for a FPSF more often than not.
The one case where I like a basement is on a sloped site where you can have a walk-out basement and really make proper, livable space.
JGSG,
"The one case where I like a basement is on a sloped site where you can have a walk-out basement"
I agree. That and a basement where the ceiling is high enough that it is only partially submerged are very different animals than the traditional one.
I have about a 3' drop with an 82' long structure. I don't like the idea of that much fill and the berm required for a mono slab. I'm guessing I just drew a .5M house.