Gov. Larry Hogan and Comptroller Peter Franchot were fuming Wednesday that the General Assembly has barred school systems from spending state tax money on portable air conditioners.The General Assembly also put an end to the annual "beg-a-thon," in which local school superintendents appear before the Board of Public Works to ask for more construction money. Hogan said the provisions were major reasons he decided not to sign the capital budget bill, where lawmakers made both changes. The bill will become law without his signature."It's one of the most absurd and ridiculous things I've ever seen the legislature do," Hogan said. The provisions were adopted by a House-Senate conference committee that met last week to resolve differences between the two chambers' versions of the state's annual budget for construction projects.Franchot complained that neither measure was aired in hearings during the legislature's 90-day session and weren't in earlier versions of the bill. He suggested that the move was made secretly and was a shot at him and Hogan."

I think it's a bizarre use of the conference committee," Franchot said. "I don't know who put that language in. Nobody's raised their hand and said, 'I did it.'"Del. Adrienne Jones, a Baltimore County Democrat who chairs the House capital budget subcommittee, said lawmakers felt that Baltimore City and Baltimore County were making sufficient progress on adding central air conditioning, so it wasn't necessary to spend state tax dollars on portable units that won't last.We're looking at being the best stewards of public money," Jones said.Jones rejected any suggestion that the decision was made in secret. "These are open meetings. Doors are open, anyone can come," said Jones, who led the House negotiators.While conference committee meetings are open to the public, it can be difficult to determine when and where they will be held. Neither Jones nor Sen. James E. "Ed" DeGrange Sr., her Senate counterpart, knew where the language they adopted originated.For several years, Franchot has pressed local school systems — particularly those in Baltimore city and county — to speed the installation of air conditioning in public school classrooms.

Hogan has joined the comptroller in pushing for the installation of portable window units as a quicker solution.But the school systems in the city and county have preferred to spend their money on central air conditioning.While that takes more time and money to install, school officials contend it is a better use of taxpayers' dollars in the long term.Franchot said the legislature's action does a disservice to Maryland families."What about the 40,000 children in Baltimore City and Baltimore County who sit in sweltering hotboxes without air conditioning?" he said.The Board of Public Works did not require money be spent on portable air conditioners but voted in January to scrap a policy that prevented state money from being spent on portable units in classrooms. The legislature's budget provision undoes that action.Baltimore County did not plan to use state money for portable air-conditioning units, even after the policy was changed, said Ellen Kobler, a spokeswoman for County Executive Kevin Kamenetz.The best way to remedy hot classrooms is to install central air conditioning during major renovation projects, Kobler said.

The county aims to have central air conditioning in all schools by 2019.At the beginning of the school year, 48 schools in Baltimore County did not have air conditioning.Baltimore City school officials did not respond to a request for comment. The city school system has been studying the feasibility of installing portable air conditioners, which officials have estimated would cost about $17 million.ac unit sun coverDeGrange, an Anne Arundel County Democrat, noted that jurisdictions are free to use their own money to buy window units if they choose — as his county has done.used ac unit for saleFranchot and Hogan also objected to a provision that says local school officials can't appeal decisions from the Interagency Committee on School Construction to the Board of Public Works on how to allocate state construction money.how to determine size of central ac unit

The appeal process has been dubbed the "beg-a-thon" because it usually involves a full day in January when local school superintendents and other officials go before the three board members to implore them to fund their projects.Last month, the Public School Superintendents Association of Maryland wrote a letter to House Speaker Michael E. Busch and Senate President Thomas V. Mike Miller calling the process "unnecessary and redundant.""Our experience has been that the members of the BPW often do not question the construction projects but use the time as a forum to advance political agendas such as financial literacy, declining enrollment, communications to parents, post-Labor Day starts, charter school approvals, and other instructional or operational issues," the letter said.The superintendents specifically excluded Treasurer Nancy K. Kopp — but not Franchot or Hogan — from their criticism. Kopp, they said, asks "appropriate questions."Franchot said the superintendents object to the "transparency and accountability" of the process.

He said members would still be able to quiz superintendents when they appear before the board on other school-related items.DeGrange said the beg-a-thon was an "outdated" event. "It was just a ridiculous process," he said.Your air conditioner, heat pump, or furnace probably uses a lot of energy. Heating and cooling makes up about half of the total energy use in a typical house. For air conditioners and heat pumps using electricity generated in fossil-fuel fired power plants, the amount you use at home may be only a third of the total. A question I get asked frequently is whether or not it's OK to close vents in unused rooms to save money. The answer may surprise you. The photo above shows a typical vent for an ducted HVAC system (air conditioner, heat pump, or furnace). On the return side, you'll typically see plain grilles, but on the supply side, where the conditioned air gets blown back into the house, most HVAC contractors install registers like the one above. It has a lever of some sort that allows you to adjust the louvers behind the grille.

You'd think that since it's adjustable, it must be OK to open or close it to suit your needs, right? The blower in your HVAC system is the heart of the air distribution. It pulls air from the house through the return ducts and then pushes it back into the house through the supply ducts. In high-efficiency systems, the blower is powered by an electronically commutated motor (ECM), which can adjust its speed to varying conditions. The majority of blowers, however, are of the permanent split capacitor (PSC) type, which is not a variable speed motor. In either case, the system is designed for the blower to push against some maximum pressure difference. That number is typically 0.5 inches of water column (iwc). If the filter gets too dirty or the supply ducts are too restrictive, the blower pushes against a higher pressure. In the case of the ECM, a high pressure will cause the motor will ramp up in an attempt to maintain proper air flow. An ECM is much more efficient than a PSC motor under ideal conditions, but as it ramps up to work against higher pressure, you lose that efficiency.

You still get the air flow (maybe), but it costs you more. The PSC motor, on the other hand, will keep spinning but at lower speeds as the pressure goes up. Thus, higher pressure means less air flow, and, as we’ll see below, low air flow can cause some serious problems. The important thing to remember here is that no matter which type of blower motor your HVAC system has, it's not a good thing when it has to push against a higher pressure. In a well-designed system, the blower moves the air against a pressure that's no greater than the maximum specified by the manufacturer (typically 0.5 iwc). The ideal system also has low duct leakage. The typical system, however, is far from ideal. Although most systems are rated for 0.5 iwc, the National Comfort Institute, which has measured static pressure and air flow in a lot of systems, finds the typical system to be pushing against a static pressure of about 0.8 iwc. Now we're ready to address the question of closing vents.

When you start closing vents in unused rooms, you make the duct system more restrictive. The pressure increases, and that means an ECM blower will ramp up to keep air flow up whereas a PSC blower will move less air. Most homes don't have sealed ducts either, so the higher pressure in the duct system will mean more duct leakage, as shown below. The more vents you close, the higher the pressure in the duct system goes. The ECM blower will use more and more energy as you do so. The PSC blower will work less but not move as much conditioned air. In both cases, the duct leakage will increase further. In addition to moving air, your air conditioner, heat pump, or furnace is also cooling or heating that air that flows through the system. The air passes over a coil or heat exchanger and either gives up heat or picks up heat. In a fixed-capacity system—and most are—the amount of heat the coil or heat exchanger is capable of absorbing or giving up is fixed. When the air flow goes down, less heat exchange happens with the air.

As a result, the temperature of the coil or heat exchanger changes. If air flow is low, it'll dump less heat into the coil in summer, and the coil will get colder. If there's water vapor in the air, the condensation on the coil may start freezing. You might even end up with a block of ice, as shown in the photo below. And ice on the coil is really bad for air flow. It's also bad for the compressor as not all of the refrigerant evaporates and liquid refrigerant makes its way back to the compressor. If you want to have to buy a new compressor, this is a good way to do it. Same thing if you have low air flow over a heat pump coil in winter. You could get a really hot coil, high refrigerant pressure, and a blown compressor or refrigerant leaks. Similarly, low air flow in a furnace can get the heat exchanger hot enough to cause cracks. Those cracks, then, allow exhaust gases to mix with your conditioned air. When that happens, your duct system can become a poison distribution system as it could be sending carbon monoxide into your home.

Let me now summarize the problems I've described above that can result from closing vents in your home. The first thing that happens is the air pressure in the duct system increases, which may give rise to these negative consequences: You're not guaranteed to get all the problems that apply to your system, but why take the chance. I recently wrote about all the IT folks who are trying to follow in Nest's footsteps and profit from the home energy efficiency movement. I used the Aros smart window air conditioner as the example of companies that think you can solve problems just by creating a product with a smartphone app. Well, meet a more malignant idea: the E-vent. (You can find it easily enough by searching on the term "Kickstarter E-Vent.") It's just a Kickstarter project right now, and maybe it won't get funded. If it does get funded, however, it will be subject to all the problems I described above. It doesn't matter whether you close the vents by getting up on a ladder in your home or from the beach in Cozumel.

It's still a bad idea. The E-Vent page on Kickstarter says they monitor the air temperature and open vents if the temperature gets too cold while air conditioning or too hot while heating. Of course, that’s not going to work unless they monitor the temperature right at the coil or heat exchanger. And that still probably wouldn’t work because there’s a wide range of acceptable temperatures for different systems. This is an HVAC product developed by people who don't know some very important principles of heating and air conditioning. Let's hope they don't kill anyone. The fundamental problem here is that closing supply vents in your HVAC system changes what comes out in particular locations. It doesn't change what the blower is trying to do. Nor does it change the amount of heat the air conditioner, heat pump, or furnace is trying to move or produce. It's possible you may be fine closing a vent or two in your home, but it will depend on how restrictive and leaky your duct system is.

If it’s a typical duct system with 60% higher static pressure than the maximum specified, closing even one vent could send it over the edge. If it’s a well designed system with low static pressure and sealed ducts, you shouldn’t have a problem as long as you don’t try to close too many. The only way something like this could work is if closing a vent signaled the blower to move less air and the air conditioner, heat pump, or furnace to move or produce less heat. (Properly designed zoned duct systems do this by using variable speed ECM blowers with multi-stage systems.) Otherwise you're subject to those 7 unintended consequences, one of them potentially deadly. The Sucking and the Blowing — A Lesson in Duct Leakage- Understanding Air Leakage 4 Ways a Bad Duct System Can Lead to Poor Indoor Air Quality Thanks to Curt Kinder, David Butler, John Semmelhack, Eric Sandeen, and Dale Sherman for suggestions in the comments below that made this article better and more complete.