HRV noise levels
I am trying to pick an HRV that will be hung from trusses in the conditioned attic directly over the guest bedroom – so noise is a concern. Looking at units from the usual (affordable) suspects – Broan/Venmar, Fantech, Lifebreath – with ~110-120 max cfm. I am unable to locate ANY operational noise level information, and when i contacted the manufacturers they all declined to share any noise measurement information. Fantech told me their “HERO” lines are quieter than their VHR/SHR line, but that was about it.
Does anyone have a link to a website with noise data for these, and/or other HRV manufacturers? Absent that, first-hand knowledge would be welcome if any of you can share!
thanks,
Rob
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Rob,
The HRV at my home is installed in a utility room adjacent to the master bathroom. The unit hangs from the ceiling just on the other side of the bathroom wall. There has been very little noticeable noise from the unit. I have never seen decibel specs for any units, so I don't believe noise calculations have been done on them. I currently use a Fantech unit and it is very quiet. I would imagine if your unit was installed above a bedroom in the attic, it would hardly (if any) any noticeable sound. They are generally very quiet from the ones I've seen.
Just make sure when you hang the hrv that you acoustically isolate it from the framing. I think vibration is potentially a bigger concern than machine noise. Mine has a metal track screwed to the framing and inside is a rubber piece that the bolts holding the hrv attach to.
Our HRV (Broan/Venmar 160TE) is installed in the basement below the master closet. That half of the basement is unfinished with nothing on the bottom of the floor TJI's. On low speed it cannot be heard on the first floor- can barely hear it even when standing right next to it. On high speed I can hear a fairly quiet, but noticeable, hum/drone in the master bedroom and corner bedroom. It's quieter in the other bedroom and can barely hear it at the end of the hall. Can't hear it in either of the bathrooms. See the attachment for reference, the footprint of the house is 30' x 50'.
There is a timer control in each bathroom and the kitchen. Only really gets kicked into high speed for 20 minutes for showering/bathing. Rarely activated from the kitchen since the range hood does an excellent job. One final point, we really don't spend any time in our bedrooms except for sleeping so we really don't notice it operating.
If your budget allows, I recommend an oversized unit with an ECM variable speed motor, run at low speed. That will give you lower noise for a give airflow, and will also give you the option to temporarily boost the speed to a high enough level that you don't need exhaust fans in the bathrooms and rarely need the exhaust fan in the kitchen.
Isolated hangers such as what Stephen has shown is the way to go.
Most of the noise from HRVs comes air flow which you would only hear in the ducts. The bit of vibration from the unit can transfer into the structure but the spring hangers take care of most of that.
If you do have a short feed from the unit to the bedroom bellow, it is a good idea to add an S bend of flex duct or an in-line silencer to it to reduce noise.
+1 on ECM blowers. Much quieter and use about 1/2 the electricity of a standard blower. This adds up on a unit that runs 24/7.
Ahh... budget. At this point in the project, it's more of an issue than i'd like it to be, at least partially because the HVAC cost so much.
The ducts are all 6" hard pipe except for the last 1-3 feet that will connect to the HRV. Registers are all 6x12, so duct noise shouldn't be a big issue. I am glad to hear that the mechanical noise isn't a big issue for the either the Fantech or Broan/Venmar units; I still wish the manufacturers and/or HVI would post some standardized sones or db @ some standard distance for these units; seems like a reasonable thing to do even if the noise isn't a huge issue.
I was planning to use the chains/springs method of hanging the HRV; more information on the isolation mount would be welcome.
Thanks for the input, all!
Rob
Just put my system at high speed. The noise is definitely coming from supply to the corner bedroom. There are about 2-3' feet of flex duct to the 6 " round galvanized trunk. Then another 2-3' before the take off for the corner bedroom. Corner bedroom supply is mounted high on the bed/master closet wall, roughly 5' from the exterior wall (refer to the floorplan in the previous post).
My system is mounted with chains from the floor joist to springs at each of the corners of the HRV. Seems it is doing a good job with isolation- practically no vibration felt in the chains or floor joists.
Further details, no dedicated exhaust fans in the bathrooms, everything runs through the HRV. Dedicated kitchen exhaust via range hood though. Did one before with recirc range hood and just couldn't handle much more than sauteeing vegetables. Ultimately had to rely on HRV to exhaust cooking odors/fumes and it took a while. Also mine is set to operate on low speed for 30 minutes every hour- closer to the Lstiburek exchange rate than ASHRAE.
Based on advice from this thread and elsewhere on GBA, I picked the new 160CFM Broan AI unit with an ECM motor for energy efficiency and quiet operation. The good news is, the newly-installed unit doesn't make a lot of motor/fan noise - but the SYSTEM is excessively noisy: I don't hear much noise in the attic where it's installed, maybe +/- 40db; but the noise in each of the bedrooms is much louder - so much so that sleeping would be affected.
This installation pulls stale air from the enclosed and sealed crawl space and exhausts it to the outside. Fresh outside air is delivered to 3 bedrooms through 6x14" ceiling registers, and the ductwork is all dedicated 6" hard pipe. The Broan HRV is self-balancing and there are no error codes indicating airflow or balance issues; based on ASHRAE and Building Science calcs, I set a minimum of 50cfm and a max of 110.
Regardless of the air flow setting, there is a lot of whooshing going on. There is NOT a lot of air flowing of the registers (which makes sense, given the low CFM levels split 3 ways), so it isn't excessive volume. Nor does it sound like motor noise; it's more like the hard duct is amplifying the sound of the air being delivered from the HRV.
It took a lot of work to get these ducts in place, but we can't live with the system as it currently is performing so i am hoping for advice on the best way(s) to mitigate the problem. Is it simply that the ducts are too small? Or that there is no flex/insulated duct anywhere in the attic? I hired a licensed AC pro to help me install the system, but he's an installer, not a designer - so would appreciate thoughts and advice before I get him back to make things better.
thanks,
Rob
Could be a couple of things. Most likely the sounds like you are hearing the airflow noise from the blowers.
You can replace part of the fresh air supply ducting and install a length of flex anywhere after the unit. If you want even more sound attenuation, you can get a duct silencer. Something like Fantech LD6 does wonders for blower noise.
Another source could be any balancing dampers close to the supply register. If some of them are near fully closed, it can create a lot of turbulence and noise. If that is the case, change the dampers to either butterfly or iris ones. These tend to be much quieter.
Quick update: decided to try Akos' suggestion and installed a Fantech 6" silencer between the HRV and the first wye in the hard pipe (using rubber-insulated pipe clamps to minimize noise through that connection). Worked wonders: noise, while still audible at the 120cfm setting, is entirely tolerable while at 60cfm it's a whisper - about the same as a 110 cfm Panasonic Whisperfan at 50 cfm. All good; I suspect I could do even better by isolating each register, but the client is happy as it is.
No balancing dampers in the ducts, although (in hindsight) there probably should be.
Here's a thought: this is a conditioned attic space, and I don't actually need to get air into the bedrooms: nighttime temps here allow open windows all year round so, posssibly excepting wildfire season, the HVAC is never on at night. Maybe I should just dump all the fresh air into the attic and put a register into a hallway ceiling to give this air somewhere to go? That would keep all the noise in the attic...
Downside?
Anyone ever find a good resource for noise ratings or comparisons on HRVs like the Fantech HERO and Broan AI units?
My Broan AI unit is very quiet. I only hear a small amount of air noise at exhaust and intake.
I did not hang mine. I put silicone half sphere stick on feet on the bottom and it sits on a couple blocks on top of my knee wall subfloor.
Very useful, thanks!
So I ended up going with the Broan 165 HRV, and it's wildly loud at the first air exhaust register (2-3x more grind rumbling sound than at the actual HRV in the basement) and audible in all other rooms via the supply registers. It's all hard pipe and mounted to a cement halfway in my basement, so I'm wondering if a 12" section of flex on all of the inlets/outlets would help. I'm curious if you have flex in your line?
Maybe relatedly, I am only able to get a max flow of ~ 129 CFM, despite it being a ~ 160-rated unit and using 5-6" hard pipe throughout the whole system. Have you been able to get your full CFM rating? My next step is to check the systems static pressure and check it against the CFM tables provided in the manual, but I don't own a manometer.
Zehnder has detailed noise specs for all their ERVs and HRVs.