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My New Studio Build (perhaps overly detailed)
- Thread starter silky smoove
- Start date
HRV mounted
Heat exchanger installed
Panel closed
Oh... also this...
The ducts aren’t perfectly round, which is something I noticed immediately upon unboxing them. I either need to widen the interior hole slightly, or clip the fan blades a tiny bit to provide clearance. I’m not confident that the ducts will maintain a perfectly round shape, so I’m going to take it down and see if I can access the fan blades without needing to fully dismantle the fan assembly.
Heat exchanger installed
Panel closed
Oh... also this...
The ducts aren’t perfectly round, which is something I noticed immediately upon unboxing them. I either need to widen the interior hole slightly, or clip the fan blades a tiny bit to provide clearance. I’m not confident that the ducts will maintain a perfectly round shape, so I’m going to take it down and see if I can access the fan blades without needing to fully dismantle the fan assembly.
Success! The fans are mounted to the motors with a little spring clip that simply pushes on and pulls off.
Problem solved! I trimmed down the fan blades with a set of lineman dikes, and then used the file from yesterday to de-burr everything. It’s now running nearly silently. On speed setting 1, which is where I’ll leave it perpetually, I was only able to measure an ambient noise increase of 1dB (slow response, A-weighted) when I was within a foot of the unit. With my dB meter pressed against the unit I could only get an increase of 2dB. That’ll do!
The outdoor vent covers provided by the manufacturer don’t fit. Tolerances are clearly not this company’s strong suit. It’s probably fine considering I’ll need baffle boxes mounted on the exterior wall to maximize isolation. I’ll be researching them heavily next week.
Will you bring these issues up with the company? Seems to me it’s worth making a stink about, might at least get a partial refund. Just don’t tell them you circumcised those fan blades.
I suspect attempting to do so would be a lot of work for no return. I’ll think about it, but probably won’t bother.
There's probably a sticker somewhere saying "Warranty void if circumcised".
Since I'm going to have to build baffle boxes for the intake and exhaust I've decided to remove the ducts that I just installed and instead use lined flex ducting instead. It will reduce the bridge between the inner and outer leaves on the north wall. I need flex ducting for the baffle box anyway, so I might as well carry it all the way through to the HRV itself. Now to find some that are appropriately sized.
Winner winner, chicken dinner. I'll have to cut off the jacket at the points where it passes through the inner and outer leaves, but otherwise this should work well.
5 in. x 25 ft. Insulated Flexible Duct R6 Silver Jacket-F6IFD5X300 - The Home Depot
5 in. x 25 ft. Insulated Flexible Duct R6 Silver Jacket-F6IFD5X300 - The Home Depot
Put out the call for a local HVAC tech to finish off the mini split, and have requested the my electrician get me on his schedule for final trim-out ASAP. I’m following up with the door guy I’d like to use tomorrow. Getting close!
I’ve used that sort of ducting to route air conditioning. Worm gear clamps over plastic end pieces worked well. A problem I encountered was condensation inside the duct. Hopefully, it won’t be an issue for your application.
I think that the baffle design is going to take a lot of homework to figure out.
I think that the baffle design is going to take a lot of homework to figure out.
They’re surprisingly simple... to design. Hopefully the execution isn’t too bad.
I once built one with 18mm (¾”) baltic birch. I wound up building a jig so that I could use a router to cut dado’s that the baffles would slide into. It went together well and was glued and clamped. No nails or screws were used. It was very solid.
It turned out to be very heavy and was mounted with steel angle brackets. It was inside so it didn’t have to brave outdoor weather conditions. I’ve seen inline units that were made out of galvanized steel ducting. A lot lighter.
It turned out to be very heavy and was mounted with steel angle brackets. It was inside so it didn’t have to brave outdoor weather conditions. I’ve seen inline units that were made out of galvanized steel ducting. A lot lighter.
A galvanized steel assembly is something I’ve considered to keep the weight down, but just like all other things in the sound isolation world, mass matters. The current plan is a plywood and Green Glue sandwich skinned with something that looks nice and will be weather-resistant. I full expect it to be heavy, but if I can lag it into the building studs it should be fine.
Four wire conductor cable connected from the air handler to the condenser unit.
What are these baffle boxes Silky? You've mentioned them, but I can't seem to find or imagine what exactly they are/do. I find myself drawn to pondering up a solution.
It's a way of making the ventilation side of an HVAC system quieter, and ideally in both directions (intake and exhaust). There are a number of designs ranging from full blown dead vents, to mechanical silencer boxes that utilize frequently turning and size changing ductwork, to inline mechanical solutions, all the way down to the humble baffle box, which is what I will be using. The idea is to make the flow path for air and sound less straight, more irregular, utilize changing cross-sectional areas (which is how a gun silencer works), and ultimately minimize the impacts that fresh air ventilation create on a sealed up sound isolation assembly.
People with more extreme isolation needs will often have one of these inside the building and one outside the building on each side of the ventilation system. Additionally, some folks will go as far as building decoupled chases through the wall assembly between the baffle boxes to achieve maximum isolation.
Below is an image of something similar to what I'll be building. Mine won't be quite this tall, and there will be one for each side of the ventilation system. Since the separation between intake and exhaust is about an inch I'll just build a single box with a dividing baffle to separate the two. This gets mounted to the outside of the building wall where the HRV's ductwork punches through. The idea is that you're creating a longer and more complicated flow path for the air to enter and exit the system. You seal the whole thing up, dress it up to look good on the outside of the building, mount an appropriate vent cover on each side to keep moisture/wildlife out of it and you should see a marked increase in isolation. My simple design will net me about 3.5' of duct length, two 90-degree bends, and three 180-degree bends for sound to navigate. I'll be constructing with two layers of plywood with Green Glue in between to add some damping to the equation. I haven't nailed down the size yet as I have to calculate the amount of loss the HRV will incur as a result of having to push/pull air through this more complicated system (i.e. the unit was more or less only designed to go straight through a wall in as short of a run as possible).
It seems like that could be built with much lighter materials; 1" EPS foam insulation baffles come to mind, or 1/4" ply panels. There should be very little structural load on any of the components, so if you're looking to save weight, there appear to be options.
