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Show HN: I built an under-the-door fan duct to lower bedroom CO2

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Re: Show HN: I built an under-the-door fan duct to lower bedroom CO2

#11

Post by turtlebits »

bizzz wrote: post #8
turtlebits wrote: post #3

Generating negative pressure in a room isn't great for fresh air. You'll be sucking air through any opening- wall outlets, floor registers, ceiling light fixtures, gaps in baseboard trim, etc. Might be simpler to augment your fresh air intake with a fan.

Good point for standalone houses! I live in an apartment, so everything you listed is backed by some concrete blocks. So, realistically speaking, the air in any meaningful amounts can only come through the window/trickle vent of the door.

You'd be surprised where air can leak in. Your house/building is not a closed system. You should assume that any/all wall penetrations will infiltrate air, via electrical wiring/conduit, through insulation, plumbing, hvac ducting.

Re: Show HN: I built an under-the-door fan duct to lower bedroom CO2

#12

Post by nancyminusone »

Software people will do anything but learn to use traditional CAD...

Just kidding. But would you mind sharing what you find so compelling about CadQuery?

As a mechanical person, these code to CAD tools make as much sense to me as suggesting you should write programs with a compass and straight edge.

Re: Show HN: I built an under-the-door fan duct to lower bedroom CO2

#13

Post by robbles »

nancyminusone wrote: post #12

Software people will do anything but learn to use traditional CAD... Just kidding. But would you mind sharing what you find so compelling about CadQuery? As a mechanical person, these code to CAD tools make as much sense to me as suggesting you should write programs with a compass and straight edge.

I've used OpenSCAD for a few small projects. The main draw for me is avoiding all the "fiddly mouse stuff". I figure it's a trade-off between simple stuff being more complicated, and complicated stuff being easier to bulk edit and organize.

Re: Show HN: I built an under-the-door fan duct to lower bedroom CO2

#14

Post by ahaucnx »

amluto wrote: post #7

Given the effort involved (unusually-shaped 3D printed duct and housing for the whole gizmo), ISTM it would make a lot more sense to fit the duct to the trickle vent and operate it in positive pressure mode. This would have lots of advantages: - With positive pressure, the intake air doesn't pick up contaminants from the wall cavities and other nooks and crannies within the building envelope. - A fresh air supply fan…

Running a positive pressure system in my house since many years, I agree that sucking in fresh air from outside and filter it with a HEPA filter makes more sense.

You probably need to make sure you use a fan that creates enough pressure to get the air through the trickle vent as well as a filter. A duct fan might be more suitable than a PC fan for this.

Re: Show HN: I built an under-the-door fan duct to lower bedroom CO2

#15

Post by ajb »

nancyminusone wrote: post #12

Software people will do anything but learn to use traditional CAD... Just kidding. But would you mind sharing what you find so compelling about CadQuery? As a mechanical person, these code to CAD tools make as much sense to me as suggesting you should write programs with a compass and straight edge.

Mainly, that all the data (constraints etc) are discoverable in one place instead of hidden behind various gui features. Also being able to use a battle tested version control system like git instead of whatever ball of duct tape comes with the tool.

Re: Show HN: I built an under-the-door fan duct to lower bedroom CO2

#16

Post by ahaucnx »

Achim, founder of AirGradient here.

Nice to wake up and see a hacker news post benefiting from our open source air monitor designs, especially with the original design that we started with so many years ago! Makes me realize how much AirGradient developed since these early days.

Did you consider linking the fan with the CO2 data and making this a demand controlled system? Like you control the speed (or just switch on / off the fan) based on CO2 levels?

I think this could have a few advantages in terms of energy savings, noise level etc.

Re: Show HN: I built an under-the-door fan duct to lower bedroom CO2

#17

Post by amluto »

ahaucnx wrote: post #14
amluto wrote: post #7

Given the effort involved (unusually-shaped 3D printed duct and housing for the whole gizmo), ISTM it would make a lot more sense to fit the duct to the trickle vent and operate it in positive pressure mode. This would have lots of advantages: - With positive pressure, the intake air doesn't pick up contaminants from the wall cavities and other nooks and crannies within the building envelope. - A fresh air supply fan…

Running a positive pressure system in my house since many years, I agree that sucking in fresh air from outside and filter it with a HEPA filter makes more sense. You probably need to make sure you use a fan that creates enough pressure to get the air through the trickle vent as well as a filter. A duct fan might be more suitable than a PC fan for this.

The pressure drop across a HEPA filter is a function of flow rate per unit area (i.e. velocity), and it can be very very low if the velocity is low. You only need some 15 cfm per person, which isn't very much. The real issue that that a HEPA filter that will achieve extremely low pressure drop is rather bulky.

Re: Show HN: I built an under-the-door fan duct to lower bedroom CO2

#20

Post by JayStavis »

bizzz wrote: post #10
JayStavis wrote: post #4

I wonder what the market size for this is. If it were a real product that wasn't super ugly in the bedroom, we'd use it. My BR is ~1500 ppm with two sleepers in a 10x12 room, and opening the window isn't an option.

Heh, never really thought there's a market for it. Though now I can imagine it being sold at some TV shopping channel. A solution to a problem you never knew you had. Anyway, I think there are plenty of people who do not want to open windows and still have fresh air. But the amount of people who can't modify their room or for whatever reasons don't want to open their bedroom door is bound to be much less. Now I'm cur…

We don't like to open the door because of habit, light leaking, and noise.
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