Green Building

Ventilating a Home in Cold Weather

Prime:  prime Subtitle:  You need fresh air, but bringing in cold outdoor air can cause problems Images: 

When I woke up Saturday morning, the temperature outdoors was -40 degrees. The wind chill was -100 degrees! It was just unbelievably, impossibly, inhumanly cold outside. Fortunately, that was on a mountaintop in New Hampshire and not where I was. I happened to have woken up on a mountaintop in North Carolina, where the temperature was a much warmer -3°F.

read more

Night Surveys: The Lights Are On, But Nobody is Home

Subtitle:  How Yale University's energy manager uses after-hours walk-throughs to save energy Images: 

Julie Paquette has been Director of Energy Management at Yale University for about 6 years. That means the buck stops at Julie’s desk for the energy consumption of over 400 buildings on campus. Yale has a pretty sophisticated approach to energy, including the Yale Facilities Energy Explorer, an energy dashboard system that shows energy consumption and details for every one of those 400 Yale buildings.

read more

The Buy-in Problem

Prime:  prime Subtitle:  From code compliance to Passive House certification, getting good work from contractors is hard Images: 

Last week I read a nice little article by Steve Baczek about getting buy-in from the various stakeholders involved with building a home. He's an architect who works closely with the people who build the homes he designs. He's also a former U.S. Marine who understands the importance of what he calls "a ladder of leadership and responsibility."

read more

Exterior Insulation on 2x4 Walls Versus 2x6 Walls With Cavity Insulation Only

Prime:  prime Subtitle:  A look at some modeling results may help you decide Images: 

If you live in the world of 2x4 walls, as I do, you may have wondered about the savings you'd get by going to a more robust wall assembly. The typical house in southern climes has 2x4 walls with R-13 insulation in the cavities. The two ways to beef that up would be to add continuous exterior insulation or to go to a thicker wall. But which saves more energy? And how do they compare to the plain old 2x4 wall?

read more

How Does a Heat Pump Get Heat From Cold Air?

Prime:  prime Subtitle:  The physics of heat pumps isn’t really that difficult to understand Images: 

Cold weather is coming back to Atlanta this week, so let’s talk about heat. An increasingly popular way to heat buildings these days is with heat pumps, even in cold climates. But how do they work?

read more

Extending the Reach of a Moisture Meter

Subtitle:  Simple ways to measure moisture content deeper into building assemblies Images: 

Typical pins on moisture meters are ½ inch long, meaning you can only determine moisture content by weight near the surface of building assemblies and materials (including wood, gypsum wallboard, and concrete). But I often find myself needing to assess moisture content of first condensing surfaces in walls and ceilings or well below the surface of basement slabs.

This article looks at ways to extend the reach of a moisture meter. (For introductory information on moisture meters, see Tools of the Trade: Moisture Meters.)

read more

Two Rules for Humidity

Prime:  prime Subtitle:  To prevent moisture damage from humid air, just do these two things Images: 

Because I've written so much about moisture in buildings, I get a lot of questions on the topic. Some are about walls. Some are about the attic. Some are about windows. Some are about the crawl space (which generates the most questions on this topic).

The key to answering a lot of those questions boils down to an understanding of how water vapor interacts with materials. Once you know that, it's easy to see the two rules for preventing damage from humidity.

read more

The Four Laws of Thermodynamics

Prime:  prime Subtitle:  We often talk of the second law, but what are the other three? Images: 

Building science is an odd subject. Few colleges and universities teach it. The majority of those who work on buildings call themselves engineers, architects, and contractors, not building scientists. And many of those who do invoke the term can explain at least one implication of the second law of thermodynamics (we'll get to that below) but may not know what the other laws of thermodynamics are, why their numbering is so peculiar, or even how many there are. Do you?

read more

How Many Tons of Air Does a 2.5 Ton Air Conditioner Move?

Prime:  prime Subtitle:  And under what conditions would it move exactly 2.5 tons of air? Images: 

We live in this invisible stuff called air. (But of course you knew that.) We pump it into and out of our lungs. We exhaust it from our bathrooms and kitchens. We cycle it through our heating and air conditioning systems. If we're lucky, we live in a home that even brings outdoor air inside as part of a whole-house ventilation system. But we're missing something.

read more

Water Tables and Basements

Subtitle:  How to use geologic, soil, and historical maps to keep your basement dry Images: 

When we bought our home (built in 1907), I called in a favor from an electrician friend of mine to upgrade the 60-amp to a 100-amp service. Having worked together in New Hampshire where many of our projects were on sites full of ledge, he smirked when he told me: “Here, you go try and drive this 12-foot copper grounding rod.”

read more

When Are Door Undercuts Sufficient for Return Air?

Prime:  prime Subtitle:  You don’t always need to install individual returns, transfer grilles, or jumper ducts Images: 

Most people don't know that simply closing a door in their home can make them sick, increase their energy bills, or reduce their comfort. We live in this invisible stuff called air. We pull many pounds of it into our lungs each day. A typical air conditioner, heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump., or furnace easily moves 20 tons of air a day. (Yes, I'm talking about 40,000 pounds! We'll save that calculation for another day, though.) And the simple act of closing a door changes the dynamics of a house in ways that can have profound impacts on the people inside the home.

read more

An Easy Retrofit for Return Air

Prime:  prime Subtitle:  For homes without dedicated return grilles in the bedrooms, this easy-to-install device provides a return air pathway Images: 

Your bedroom really doesn't aspire to be a balloon. Yet, because of the way your heating and air conditioning system was installed, it may be acting like one. At least to an extent. It doesn't expand the way a balloon does, but it does get blown up.

Think about it. If your bedroom has a supply register from your HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. system but no return grille or other pathway for the air to make its way back to the unit, what happens to that air blowing into the room when you close the door?

read more

Four Sources of Crawl Space Moisture

Prime:  prime Subtitle:  To stop moisture problems in vented crawl spaces, you have to know where the moisture comes from Images: 

Here in the southeastern U.S., we have a lot of crawl spaces. Most are vented. Even most new ones are vented. It's not because it's the best way to keep them dry. That's certainly not true. We have enough research on crawl spaces to know better. No, they're vented because foundation vents got into the code decades ago and, once there, they’ve been difficult to dislodge.

So if you have a vented crawl space, especially in a humid climate, it most likely has moisture problems. And where does that moisture come from? Let's take a look.

read more

The Difficulties of Third-Party HVAC Design

Prime:  prime Subtitle:  How do we get everyone on the same page? Images: 

What if a builder refused to build from plans drawn by an architect? What if a tile installer refused to implement designs handed to them and instead did their own thing? What if an HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. contractor told a potential client they wouldn't install a system designed by a third party to ACCA protocols?

One of those questions is more real than the others. Of course builders build from architects' plans and tile installers don't throw out designs they're asked to implement. But third-party HVAC design is a different animal.

read more