Sentenced to serve


Old library

Old meets new

As part of a blogging course, we were asked to define what our blog is about in one sentence. That’s not an easy task. I’d like to make it about everything that interests me, but that would dilute a lot of the building science content.

In no particular order, I’m interested in; history, animals, natural systems, reading, gardening, good discussions, cooking, photography, crosswords, brooks, appliance repair, craft beer, edge effects, woodworking, building structural analysis, education, hand tools, technology, and whatever else might strike my fancy on a particular day. If my blog was about all that I wouldn’t have time to experience any of those things. So I’ll stick to building science. But don’t be surprised to see some of those other interests make guest appearances. That’s where the second half of the assignment comes in, but that’s the next post.

Buildings remain my main interest. As I think about the 40 plus years I’ve been involved with buildings I realize that nothing has held my total interest for so long. One of the reasons is that I discovered how poorly buildings are understood. Buildings are complex, highly interactive systems. Most of us only see the smallest part of what’s going on in a building. That leaves us vulnerable to mistakes that can make us dissatisfied with our homes or offices.

My mission is to help you understand how to keep your personal habitat healthy and comfortable. That’s my sentence.

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Baby, don’t you light my fire

I don’t venture into energy policy too often. There are more traps and mistaken concepts than I care to navigate. But occasionally you’ll find me dipping my toes into those muddy waters, this is one of those times.

A recent blog post by David Roberts argues that we can only get to zero carbon energy via electricity. There are bits you can quibble with around the edges (direct water power and solar steam) but he’s right. Based on what we know about using and delivering energy, electricity is the best option to de-carbonize our world. It won’t be easy, but it is possible to envision a carbon free electrical grid.

This isn’t a brand new concept. We’ve been talking about the need to modernize the grid to handle distributed generation for over a decade. I remember having this discussion at a conference in the late 1990’s. The country is also going to have to come to terms with how we are going to move this electricity long distances too. No one likes power lines, for good reason. They’re ugly and disrupt forest ecosystems. But until we figure out how we can get the electricity from one place to another we’re stuck in place.

Zero carbon is a laudable goal in its own right, but there is at least one vitally important reason to stop burning stuff. That stuff is too valuable for other things. Like petroleum, you can do a lot with that stuff. Besides burning oil, there are probably many other things we shouldn’t do with it. Chemical fertilizers seem to be counterproductive in the long run, but replacing oil based grease with animal fat doesn’t strike me as a good option. Several pharmaceuticals wouldn’t exist without petroleum. AIDS drugs among others are built on molecules from oil.

I don’t envision a petroleum-free world, there are too many beneficial things we get from oils to give it up entirely. But burning it? John Straube of RDH Building Science Inc once said that future generations would be horrified that we would burn such a useful material.

As a species, we have gotten into the bad habit of adding energy to solve problems. Instead of going after vigorous source control we run energy intensive filters and dehumidifiers. We also are too enamored of lighting things on fire. The list of problems from combustion is long and varied. You’ll undoubtedly see posts about the problem with burning things in your home from me before too long.

I know that I won’t live to see the end of fire. The romance and infrastructure around combustion aren’t going away soon. But we should be thinking seriously about it. And planning, that will help too. And put down that match.

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Attic adventures #1: Insulation is where you find it

Something new, I’m going to be adding an occasional post about oddities and adventures in building science. Funny things do happen and I’ll be sharing them with you.

I’m a New Englander born and bred. Grew up on a farm and everything. I learned to admire the thriftiness and ingenuity of those old Yankee farmers. Never buy a new baler when you can put a working one together from the three broken ones behind the barn. Something thrown out is many things wasted.

That spirit continues. Sometimes it gets out of hand and you get a hoarder. Usually you find a clever old soul who has managed to repurpose stuff in a clever way and has come out way ahead. But sometimes…

Many years ago I was called to an old house in a small NH town that’s known for being a small NH town. Definitely Yankee territory. The house was a simple farm house, a rectangular shape, two stories and a steep, pitched roof. The complaint was high energy bills, so I went prepared to investigate.

Part of the problem was that the house had been converted to electric heat. Baseboard placed around the perimeter, cheap to install, expensive to operate. The previous owner who did this clearly wasn’t a good Yankee. The woman who owned it now was trying to find a way to lower the cost without a huge investment in a new heating system.

We started a walk through the house and I found that the walls weren’t well insulated and a few windows needed weatherstripping. This was my pre- thermal imaging days, so I had to do more poking into things, but an old house with holes in the walls is pretty easy. We got to the second floor and I asked how to get into the attic. “You’ll have to ask my son” I was told. “He’s the only one who goes up there, to insulate.”

That was interesting. She called her son, he lived down the road. “He’ll be along in a few minutes, he has to load his long ladder.”

The access was a cut down door that had been installed in the gable end of the house. The son had done it himself. Interesting! The ladder went up and so did I. I opened the door and shone my flashlight in and saw mattresses, mattresses everywhere. There were twins and doubles, kings, queens and every odd size you could imagine. They were placed, though not carefully, over the entire attic floor.

Unfortunately there were large gaps between the mattresses which made any insulating value useless. Worse, the mice, chipmunks, and squirrels were moving in. They chewed holes for nests, stored seeds and nuts, and, uh, eliminated. It was disgusting, not to mention an incipient health hazard.

It seems the son ran the local dump. He had gathered all the discarded mattresses over several months and placed them in his mother’s attic to “insulate” Clever, but I can’t give the guy any Yankee points. I suggested a hazardous waste company to remove and clean, although the son took on that task as well. I hope he wore a mask.

A professional insulation company did come in. They packed the walls with cellulose and blew several inches over the attic floor as well. They weatherstripped doors and windows and the homeowner is much happier.

Remember, a nice mattress  is great for a good nights sleep, but don’t share it with the squirrels.

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Old houses are like old people. You can learn a lot from them.

One of my indulgences is taking time to look at a detail in an old house and trying to get into the head of the craftsman who made it. I can’t say that every try is successful, but when I do figure it out there have been some great “Aha!” moments. More than a few times it’s taken years and some other discoveries to see what was going on.

Sometimes it’s a structural choice; how were two pieces of wood joined, why was that support here and not there. It could be material choice or why did that window go into THAT corner. Sometimes there’s a really good, smart reason, other times it’s tough to figure and there are some clear mistakes. These are lessons that are sitting right there waiting to be learned and many of them are still applicable today.

One important thing about successful (surviving) old buildings is that they could dry out if they got wet. Quickly too. And that’s the important part, if wood stays wet it rots. If it dries quickly it’s fairly forgiving of some periodic wetting. If you let it get too wet too often your building won’t survive for future generations to see how stupid you were.

How did they dry and are there lessons about that for today? They dried because of lots of air and energy flow and materials that don’t trap moisture. No insulation and free air movement in wall cavities are a recipe for drying. Interior horsehair plaster dries very rapidly which also helped keep the walls dry. Of course in the 18th & 19th centuries showers and hot tubs were in short supply and indoor swimming pools were even rarer. So buildings had lower moisture loads to deal with and had good drying potential. That’s a good way to make a building that will last.

We have become more regular in our hygiene, and with higher energy costs we want insulation in our walls and ceilings. This puts us in a bit of a bind because we just messed up our building longevity strategy. What to do? Let’s go back to our original building and see what else we need to change. Well, if the walls won’t dry, maybe we should keep them from getting wet. Some of those old details will still work for us and some won’t. If we are expecting better thermal performance we need to give the walls (and other building parts) better water management so they can make it to the next generation and beyond.

With future posts I’ll explore the details, but new construction will have different solutions than rehab, probably. With rehab or retrofit you have to think more carefully about what the strengths and weaknesses of the building are, what the extent of the planned work will be and what can realistically be done within those constraints. The reason I love working with older buildings is that I can use all those lessons I mentioned earlier and, with luck, get some more.

Oh, one more thing. When you do undertake a rehab on an old building remember to leave a penny dated the year you completed the work where someone will find it when they get around to their own project in the future. They’ll know that you were thinking about them and maybe take the time to learn a few lessons of their own.

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How wet is too wet?

Is your house wet? Is it just damp? Or, more to the point, is it wetter than it should be?

If you have standing water anywhere in your house it’s too wet. That’s pretty easy. A leaking roof, water on the basement (or any) floor, or even standing water in an uncovered sump pit are clear indications that you have a problem. If we could stop here it would be easy, but things get more subtle and sometimes subjective as we drill down to a deeper level.

Your house can be wet in places you can’t see and in ways you aren’t aware of and that can be where the most damage happens. We’ll talk about how it gets wet in a future post. Water can hide in walls and between floors. Sometimes it’s right out in the open and we don’t see it as a problem, a hot tub, an aquarium, or wet laundry hanging in the house.  It can even be that long hot shower that causes problems.

We have to worry about water in all its states, liquid, solid and gaseous. Liquid, well that’s just water, we know what that is. Solid is ice. In that form it isn’t as problematic as liquid, but it has a tendency to turn to liquid and that’s a bad thing. Gaseous; steam, water vapor, humidity. Now this is a little trickier. Humidity can cause problems but not as many as liquid water. It can be a great clue as to the presence of water however. And there’s an easy way to measure it.

Inexpensive humidity gauges are available all over the place. They’re combined with digital thermometers and are fairly accurate. You can even get models that can have several remote sensors to monitor conditions in several areas. Depending on how your house is built and configured that can be very helpful.

High humidity can be a very powerful indicator of a water problem. Assuming you keep your house in a normal temperature range, 68F – 75F, your humidity levels should vary from a low in the mid to upper twenty percent range in the coldest days of winter to fifty percent during a hot humid period. If you cool your home during the summer your peak should never exceed 50%, the low 40% range would be better.

We’ll talk about how we came up with these numbers later, and remember that these are only guidelines. Going a bit outside these numbers for brief periods isn’t critical. What’s important is to have a general sense of what’s normal for your house. If you get a sudden change, one way or the other, you want to find out why. If it isn’t weather-related you should get to the bottom of it quickly.

Come back soon. I will be continuing this series of building science posts, hopefully on a more regular basis.

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And One To Grow On

I love water. I’ve got a nice glass of water on my desk right now. Without water you don’t have life in any sense that we earthlings would recognize. Unless you have a vacation home in another star system I think we can conclude that it’s pretty basic to life. And that is why it’s so important to make sure that your house stays dry.

All of the destructive and nasty effects that water cause in a building are because life is happening. Rot is simply fungi eating the wood in your house.  They need a certain moisture level in the wood to live, when the wood is below 20% moisture content rot is unlikely. Kiln dried construction lumber is usually specified as KD 19 or MC (moisture content) 19, meaning kiln dried to maximum 19% moisture content. It’s normally a little drier, because it’s still losing moisture as it is shipped and stored. Wood changes MC with relative humidity and usually ends up in a range between 9 and 15 percent MC unless you live in either Phoenix or Seattle where the range will be different.

There are two primary types of wood rot. One is a stringy growth that requires a fair amount of moisture and can be a little slimy. When a tree first falls in the forest this is often the first type of rot to show up because the wood is quite wet. The other known as brown rot or dry rot appears as brown rectangles of cracks and splits. Also the wood becomes powdery as it loses moisture. Dry rot is a bit of a misnomer, really there’s no such thing. It needs less moisture that the stringy type but still needs 25-35% MC. This type of rot will often appear on wood that is intermittently wet and dry. That might lead to some of the confusion. Often I have to explain to people that they just didn’t see it when it was wet. Finding intermittent water sources can be challenging.

So rot is caused by living things. Most of these living things are loosely classified as fungi. Mold is a kind fungi that grows as black spots near the shower and that cause the odors in your carpets. The types of fungi are truly uncounted, I’ve heard people throw numbers around like “hundreds of thousands” and “millions”. Most don’t bother us, some cause allergies, and a few will make you sick. A lot of the effect depends on concentration. The more water the more those little critters* will grow. Much of the health problem comes from the release of the spores as they reproduce.

The important point is that a wet house is an unhealthy house. Lower energy use makes dealing with water a bigger challenge so water control, for all states of water, is vital to maintain a healthy home and good indoor air quality (IAQ). We’ll be talking about how water gets in, how it moves around and other interesting things in future posts. For now, keep your powder (and your house) dry.


*If you gather a group of experts and ask whether fungi is plant or animal you better be prepared for a long listen. Some claim that fungi are an entirely separate life form.

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What is building science?

What’s this Building Science stuff about?

Without being too cute about it, it’s just applying science to buildings and using it to make choices. We’ve been using science for structural decisions for years. We’ve even been able to reduce a lot of these decisions to simple design tables. We know enough about how structure works that we can make good rules to cover most of the common situations. It’s been quite successful, modern buildings are structurally great. Assuming that the contractors did their part right.

Now science is being used to inform some of the trickier aspects of building performance, energy and water actions within the building. We also have to include air movement in this because both energy and water can move on air.

Why are energy and water so important? Energy because we don’t want to use too much. Insulation in new homes is mandatory. People are more aware of comfort issues (Oh, comfort! that’s several blog posts on it’s own.) and expect that their houses will provide a certain level of comfort and efficiency.

Water because it can feed the things that will destroy our homes and make us unhealthy. Those are molds of various types and also deserve more coverage than they will get in this one post. What we call rot is mold feeding on wood. Mold growing on other surfaces can lead to allergies in certain individuals. For some people this can be quite severe.

What’s the connection between energy and water? Simply, water dries (evaporates) through the use of energy. The less energy a house uses the less potential it has to dry. So water management practices become more critical the more efficient a building becomes. What makes it even trickier is that the materials we use to build houses react in very different ways to water. Old buildings use materials much different from those we use now. Remodeling can introduce modern materials that will change the way a building handles water. It’s good to know what those changes are likely to be and what needs to happen to compensate for them. Building science.

Oh, see that last sentence in the second paragraph? The details for water and air management need to be executed properly too. Uncontrolled water in an energy efficient house can do a major amount of damage and repairs can get expensive really quickly. Call me and let’s get it right the first time.

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New blog location

I’ve changed web hosts which means I’ll be able to host this blog directly on my site. Over the next few weeks I’ll be adding content and moving older items here.

Feel free to comment and ask questions. I’ll respond as quickly as time allows. I hope we can have some interesting conversations.

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