Posts Tagged With: Education

How to Ventilate Your House

Every day we learn more about the importance of good air quality. Here are some tips to help you improve air quality inside your house.

How to Measure

First, you are going to want to be able to measure air quality in your house. There are a few different things you want to measure:

  • PM2.5 measures the amount of particles that are 2.5 micrometers or smaller. Compared with larger particles, PM 2.5 does the most damage because they are so small that they can get embedded far into your lungs, which is why they are measured and tracked. You want to keep this value as low as possible.

  • AQI is an aggregate index that measures PM 2.5, PM 10 (10 micrometer particles), carbon monoxide, sulfur dioxide, and nitrogen dioxide in the air. The formula for calculating it is complicated but basically takes the largest value out of those. You want to keep this value below 50.

  • Carbon dioxide builds up in a stuffy room with no ventilation and can affect cognitive performance, make you sleepy, and have other bad side effects. 400 is the ambient air; a value over 1000 is bad.

To measure PM2.5 and AQI, I like the Temtop M10, though it's very easy to buy a more expensive piece of gear that you can connect to Wifi, or smart devices.

To measure CO2, I like the Aranet4, which can run forever on a single battery.

If you don't want to buy them, try to borrow one from a friend, or see if your library will buy them and loan them out; you'll get a sense for the ranges of air quality in your house after a few days.

When it's nice outside

The easiest case is when the weather is nice outside, and there's no fires or smoky air, and you don't live near a freeway. Open your windows! Bringing in outside air is the only way to lower CO2 counts (you can't just run an air purifier).

The best way to ventilate quickly is to open windows on both sides of your house, called "cross ventilation," so a breeze can flow from one end to the other. A good sign that this is working is that doors between the two windows are slamming shut.

If it's not nice outside

Sometimes you can't or shouldn't keep your windows open - it's too hot or too cold, or the air quality outside is too bad. If you live within 1000 feet of a freeway, you are likely breathing in polluted air almost all the time you are outside or have your windows open, which has been linked to lower birth weight, worse cognitive performance, higher rates of respiratory illness.

You are going to want to pump in outside air anyway. If it's hot or cold, you can use your AC, or your heat, which will take care of this for you, by swapping in new air and swapping out old air.

If you have either of these and can't or don't want to change the temperature, they should have a "fan" mode, which does not apply heat but will just bring in new air. You should be running this mode almost all of the time you have your windows closed.

Your heat or your AC will have a filter between the outside air and the fan. Mine is 16x25x1, and looks like this:

Filter for heating

You need to buy a good filter. Filters are rated on the MERV system, which sorts by how much particles they are supposed to catch. Your average filter will be about MERV 5. You want to buy a MERV 13 level filter, which is only a little bit more expensive but is going to be vastly better at stopping particulates.

Plan to replace your filter every 2-3 months, more if you run the fan more often, less if you run the fan less often.

You can supplement outside air with an air purifier like the Coway AP1512-HH. Each air purifier comes with a rating for how big of a room it is designed to clear; this one is for 360 square feet. When it ships to you, the filters are already in the purifier, but covered in plastic. Be sure to remove the plastic or the filters won't work.

I keep my air purifiers (we have four) on the lowest level all of the time. Note that these will be ineffective at lowering carbon dioxide levels; you need outside air for that. Plan to change the odor filter every 6 months and the HEPA filter once a year, more often if you live in a particularly polluted area.

Sources of bad air inside your house

The primary source of bad air inside your house is your stovetop. When we cook, the AQI inside our house spikes up above 300, which is worse than in Beijing. If the fan above your stove vents to the outside, you almost always want to run this at the highest level, in addition to opening your windows and doors, and running your house fan, in order to bring the air quality back to a decent level as quickly as possible.

Other sources of bad air include cleaning products and using the toilet. Understand if bathroom fans vent to the outside (they should, if your house is up to code) and run them. Open windows when you clean.

Your stove, your oven, and your shower will also make your kitchen hot, which can be uncomfortable if you are trying to keep the windows closed. On hot days consider using the BBQ instead, if you have one.

That's it

Modern homes in particular are designed not to leak any air if you don't want to. While this is good news for efficiently heating or cooling your house, it is bad news for air quality inside. Measure air quality inside your house and understand which tools are best for bringing in better air.

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Building a better home network

I finally got my home network in a place where I am happy with it. I wanted to share my setup and what I learned about it. There has never been a better time to set up a great home network; there are several new tools that have made this easier and better than in the past. Hopefully this will help you set up your home network!

My house

My house is two stories on a standard 25 x 100 square foot San Francisco lot. The ground floor looks roughly like this:

|               |                      |
|               |         |   Office   |
|    Garage     | Mudroom |            |
|               |         |-------------
|                           | | | | | |

Upstairs looks like this:

|    ___________                       |
|               |        Living Room   |
|    Bedroom    | Kitchen              |
|               |         -------------
|               |           | | | | | |

We have a Roku in the living room. My goals for home internet were:

  • Good wireless connection in every room
  • Ethernet connections in the office
  • Ethernet connection to the Roku
  • Synology network attached storage (NAS) and other external hard drives reachable from anywhere in the house

We are lucky to have Sonic Fiber internet service. Sonic comes in to a box in the garage, and an Ethernet line runs from there to the mudroom. None of the other rooms have Ethernet connections.

Initial setup

Sonic really wants to push Eero routers to everyone.1 Eero is fairly easy to set up, and Sonic collects a small fee from renting the router to you. You can extend your home network by adding more Eero's into a mesh network.

If you have a small apartment, an Eero is probably going to be a good fit. However, the mesh network was not great for achieving any of the goals I had in mind. The repeaters (Eero beacon) do not have any Ethernet out ports. It was difficult to extend the network from the mudroom to the bedroom without renting two extenders, which added about $100 per year, increased latency and lowered speeds. Further, clients on the network kept connecting to an Eero that was further away, instead of the closest one.


(NB: please don't stop reading here as I don't recommend this.) My next step was to replace the Eero's with a traditional Netgear wireless router in the mudroom. This also could not reach to the bedroom. So I bought a powerline adapter and plugged one end in near the router and the other end in the bedroom.

Powerline adapters send signal via electric current in your house. They don't offer great speeds. Devices on your network that use a lot of electricity, like laundry machines or the microwave, can render the powerline connection unusable.

There are probably better solutions for you than powerline adapters in 2020.

Extending Ethernet to more rooms

I called a cabling company about the possibility of running Ethernet to more rooms in the house. We decided the bedroom would be very easy since it's directly above the garage. It took a team of two two hours to drill a hole in the garage, run a cable up the side of the house to the bedroom, and install an Ethernet port in the bedroom. This cost about $200.

We looked at running Ethernet to other rooms but the geography of the stairs made this really tricky.

Side note: future proofing cabling

Our house has coax cables - the traditional method of getting e.g. cable TV service - running from the garage to four rooms in the house, but it doesn't have Ethernet set up. This is disappointing since it was built within the last decade.

There are two things you can do to future proof cable runs in your house, and ensure that cables can be replaced/swapped out if mice eat them or whatever. I highly recommend you implement them any time you are running cable. One is to leave a pull cable in the wall next to whatever cable you are installing. If you need to run a new cable, you can attach it to the pull cable, and then pull it all the way through from one end to the other.

Normally cables will be stapled to the wall interior, which makes them impossible to pull through. The other option is to leave cables unstapled. This will let you use the coax/other cable directly as the pull cable. In general though it's better to just leave a second pull line in the wall behind the port.

Without either of these solutions in place, running new cables is going to be messy. You can either try to hide it by running it along the exterior walls or ceiling of your house, or drill holes in the wall every few feet, pass a new cable through, and then patch up the holes.

Side note: cat 5 vs. cat 6

Your internet speed will be bottlenecked by the slowest link in the network. Be careful it isn't your cables!

There are two flavors of Ethernet cable. Category 5 is cheaper, but can only support speeds of 100 Mbps. Category 6 is slightly more expensive but you will need it to get full gigabit speeds.

The Ethernet cables that come with the products you buy may be Cat 5 or 6. Be careful to check which one you are using (it should be written in small print on the outside of the cable).


To load, your computer looks up the IP address for Google and sends packets to it. So far so good, but how does Google send packets back? Each client on the network needs a unique local IP address. The router will translate between an open port to Google, say, port 44982, and a local IP address, say,, and send packets it receives from the broader Internet on port 44982 to the client with that IP address.

What happens if two clients on your network try to claim the same local IP address? That would be bad. Generally you set up a DHCP server to figure this out. When your phone connects to a wifi network it sends out a packet that says basically "I need an IP address." If a DHCP server is listening anywhere on the network it will find an empty IP address slot and send it back to the phone.2 The phone can then use that IP address.

Generally speaking, a consumer wireless router has three components:

  • wireless radios, that broadcast a network SSID and send packets to and from wireless clients.
  • an Ethernet switch that can split an incoming Internet connection into four or more out ports. Generally this has one WAN port (that connects to your modem/ISP) and four LAN ports (that connect to local devices on your network)
  • a DHCP server.

You can buy products that offer each of these independently - a four way switch without a radio or DHCP server will cost you about $15. But this is a convenient bundle for home networks.

If your network contains multiple switches or multiple routers you need to think about which of these devices will be giving out DHCP.

Two Routers, Too Furious

At this point my network had one router in the bedroom and one router upstairs in the living room, via an ungainly cable up the stairs. So I had good coverage in every room, and the Roku hooked up via Ethernet to the living room router, but this setup still had a few problems. I didn't have the office wired up, and the NAS only worked when you were connected to the living room router.

Furthermore, I kept running into issues where I would walk from the living room to the bedroom or vice versa but my phone/laptop would stay connected to the router in the room I was just in. Because that router was outside its normal "range", I would get more latency and dropped packets than usual, which was frustrating.

How to diagnose and measure this problem

On your laptop, hold down Option when you click the wifi button, and you'll get an extended menu that looks like this.

The key value there is the RSSI parameter, which measures the signal quality from your client to the router. This is currently at -46, a quite good value. Lower than -65 and your connection quality will start to get dicey - you will see lower bandwidth and higher latency and dropped packets.

Apple devices will hang on to the router they are currently connected to until the RSSI gets to -75 or worse, which is a very low value. This is explained in gory detail on this page. Because router coverage areas are supposed to overlap a little bit, this means the connection will have to get very bad before your phone or laptop will start looking for a new radio.

Adjust the power

Generally this means that you don't want the coverage area for the router to reach to the center of the coverage area for the other router, if you can help it. If the coverage areas don't overlap that much, clients will roam to the closest router, which will improve the connection.

You can adjust the coverage area either by physically moving the router or by lowering the power for the radios (which you may be able to do in the admin panel for the router).

If neither of these works, as a last ditch attempt you can give your routers different network names. But this makes it more difficult to keep a connection when you roam from one router to the other.

Ethernet Over... Coax?

I had not managed to get a fixed connection to the office, which would have required snaking a Ethernet cable over at least two doorways and three walls. However, I heard recently about a new technology called MoCA (multimedia over coax), which makes it possible to send an Ethernet signal over the coax line from the garage to the office. I bought a MoCA adapter for each end of the connection - about $160 in total - and wired it up and... it worked like a charm!

Moca ethernet over coax connector in

The latency is slightly higher than traditional Ethernet, but only by a few milliseconds, and the bandwidth is not as high as a normal wired connection but it's fine - I am still glad to be able to avoid a wireless connection in that room.

This change let me move my NAS into the office as well, which I'm quite happy about.

Letting Everything Talk to Each Other

At this point I had a $15 unmanaged switch in the garage that received a connection from the Sonic Fiber router, and sent it to three places - the bedroom, the living room and my office. However, the fact that it was unmanaged meant that each location requested a public IP address and DHCP from Sonic. Sonic was not happy with this arrangement - there is a limit of 8 devices per account that are stored in a table mapping a MAC address to an IP address, and after this you need to call in to have the table cleared out. This design also meant that the clients on my network couldn't talk to each other - I couldn't access the NAS unless I was connected to the living room router.

The solution was to upgrade to a "managed" switch in the garage that could give out DHCP. You can buy one that is essentially a wifi router without the radio for about $60. This has the same dashboard interface as your router does and can give out DHCP.

Once this switch was in place, I needed to update the routers to stop giving out DHCP (or put them in "pass through mode") so only a single device on the network was assigning IP addresses. I watched the routers and NAS connect, then assigned static IP's on the local network to each one. It's important to do this before you set them in pass-through mode so you can still access them and tweak their settings.

You should be able to find instructions on pass-through mode or "disable DHCP" for your router online. You may need to change the IP address for the router to match the static IP you gave out in the previous paragraph.

That's it

I finally have a network that supported everything I want to do with it! I can never move now.

Garage router setup

I hope this post was helpful. I think the most important thing to realize is that if you haven't done this in a few years, or your only experience is with consumer grade routers, there are other tools/products you can buy to make your network better.

If you are interested in this space, or interested in improving your office network along these lines, I'm working with a company that is making this drop dead easy to accomplish. Get in touch!

1. I posted on the forums to get help several times. Dane Jasper, the Sonic CEO who's active on the forums, responded to most of my questions with "you should just use Eero." I love that he is on the forums but Eero is just not great for what I'm trying to do.

2. I'm simplifying - there are two roundtrips, not one - but the details are really not that important.

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Guarantee These Rights

From the Cato Institute: "I once attended a dinner discussion with a bunch of health care big-wigs. One highly educated woman — she is both an M.D. and a J.D. — began the dinner by declaring, “We need to make health care a right in this country, just as we make education a right.” Later in the dinner, she complained that her organization’s materials must be written at an 8th-grade level to be understood by their target audience. I interrupted to ask how she reconciled those two statements: if we really have created a right to education, why the poor reading comprehension? And if we create a parallel right to health care, how many people’s medical care will be stuck at an 8th-grade level? Her answer was non-responsive."

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Posner on college

From Richard Posner: "...colleges and graduate (including professional) schools provide a screening and certifying function. Someone who graduates with good grades from a good college demonstrates intelligence more convincingly than if he simply tells a potential employer that he's smart; and he also demonstrates a degree of discipline and docility, valuable to employers, that a good performance on an IQ test would not demonstrate. (This is an important point; if all colleges did was separate the smart from the less smart, college would be an inefficient alternative to simple testing."

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Coulson on Educational Standards

From the Washington Post Online: "Cementing the coalition, Sen. Christopher Dodd (D-Conn.) and Rep. Vernon Ehlers (R-Mich.) have recently proposed a bill to create a national curriculum in reading and math. The bill's supporters rightly tell us that by the end of high school, American students have fallen behind their international peers. Dodd and Ehlers use that observation to conclude that we need such a curriculum "to compete in the global economy." "But how exactly would homogenizing our curriculum and testing make us more competitive? "National standards would help propel U.S. economic competitiveness, because they would allow the country to set expectations higher than those of our international competitors," write Rudy Crew and Paul Vallas, the superintendents of the Miami and Philadelphia school districts, in a recent Education Week commentary. ..."But sports and manufacturing are competitive fields, while public schooling currently is not. Standards advocates mistakenly assume that high external standards produce excellence, but in fact it is the competitive pursuit of excellence that produces high standards. "We understand this point implicitly in every field outside of education. We didn't progress from four-inch black-and-white cathode ray tubes to four-foot flat panels because the federal government raised television standards. Apple did not increase the capacity of its iPod from 5 to 80 gigabytes in five years because of some bureaucratic mandate. And the Soviet Union did not collapse because the targets for its five-year plans were insufficiently ambitious."

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Cheap Education Quote

From Andrew J. Coulson of the Cato Institute: " would be institutionally suicidal for a monopoly school system to do a good job of teaching market economics. The very fact that we continue to have a monopoly school system is retroactive proof that market economics has not been well taught. Monopolies, after all, tend to be frowned on by the economically savvy."

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Are You F***ing Serious?

Just finished reading in the Philadelphia Inquirer about the second straight day of riots at West Philadelphia High, after a popular principal learned he was being fired in a newspaper. Some quotes from the article: "Problems at West Philadelphia High exploded last week after teachers there complained that assaults on staff in some cases were being downplayed. Initially, Vallas said he would replace James soon but he speeded the process after another staffer was attacked. On Friday, several small fires were set in the school and another teacher was assaulted during an evacuation...Two female students were arrested at the school entrance when metal detectors found a razor on one and a nail file on the other - items prohibited under the district weapons policy. More arrests are pending for two small fires that were set in lockers. The school was evacuated at 11 a.m. and again a short time later. Attendance was down to between 40 and 50 percent yesterday, said Ozzie Wright, acting co-principal. It's usually at 75 percent." And then, the kicker - "District officials hope they can calm the school today so 11th graders can take the Pennsylvania System of School Assessment, the high-stakes test that determines whether schools meet federal achievement targets." I mean, come on, who's being kidded here? What are you going to say to the kids? "Hey there, I know we've had two fires and several assaults over the past week, but we really want you to show up to fill out some bubbles on a test that has no real purpose. The standardized test tells the state how smart you guys are." My guess is the smart students are at home, watching the Wire and looking out for their own safety. If I'm a WPHS student right now, there are bigger issues than a standardized test. Sorry, Philly school staff.

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On Being an Elementary School Teacher

The NYT has a new blog up (subscription required) featuring posts from five schoolteachers from around America. Reading the last post from Mor Regev, a brand-new teacher in the Bronx, about how her attempts to discipline a student not only made him more disobedient but threw off her plans for the rest of the class. Schoolteaching is possibly the only discipline where we take brand-new teachers and throw them in a classroom with thirty (in this case, forty-two) students, with virtually no supervision or feedback. Furthermore, because teaching carries such a low salary, it is difficult to find qualified teachers for positions. There are two things which, based on my experience as a student, will most dramatically improve quality of education: improve the quality of the teachers, and have smaller class sizes. Improved technology in classrooms may be nice, but it doesn't do a thing if the teacher is horrible; indeed, it may be a bigger distraction to students. Furthermore, I highly doubt teachers in the 1940's and 50's were hindered by their lack of access to computers and email.
We can improve the quality of teachers first and foremost by raising salaries, but also by improving mentoring programs to give better feedback and introducing better sharing of lesson plans and effective techniques for handling and teaching a class of kids. Reducing class size will only be made possible by investing in more classrooms and more teachers at each grade level. The problem boils down to money, and better use of the money we spend. For now, we'll have our brand-new elementary school teachers on the verge of tears because they're trying their best, and failing, to control a class with forty-odd kids.

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Undergraduate Research

I wrote my Econ 1 professor today and asked her if there were any professors looking for research assistants. She said that professors rarely take undergraduate assistants. Fair enough. Which led me to the idea of having undergraduates form teams based on appealing ideas, and do their own research, maybe led by one or two full-time advising staff. You'd need to set up a large amount of infrastructure to accomplish this, but it has a lot of potential - it works like this: Students submit ideas, other students express an interest in developing the idea, and you form a research team. The adviser is exactly that - to advise on complex economic issues and provide guidance in producing tangible results. This would be useful, I think.

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