The best way to insulate your attic – part 2

Wow, where's that hole go?

In the first installment on attic insulation, I discussed why it can be dangerous to add insulation to your attic without air sealing the attic floor first. Moisture can slip through tiny cracks in the attic floor and lead to rotten roofs. Given this information, we walked through the process of finding and sealing all those insidious air leaks in your attic, some easy, some difficult. But finally, after fixing all these problems, you could lay more insulation down on your attic floor, more confident that doing so wouldn’t lead to a humid, moldy attic.

But what if there’s an easier way?

Whether you’re building a new house or retrofitting an older one, you can make life much easier on yourself by using professionally applied spray foam insulation that air seals and insulates in one shot. There are two ways of doing this, each with their own benefits and disadvantages. We’re going to review both methods. One is spraying foam on the attic floor, instead of using loose fill or batt insulation. The other is spraying foam under the roof deck. Continue reading


What does it mean if your fiberglass insulation is black?

Insulation filters the air leaks from your house, showing you signs of energy loss

You might have noticed some black insulation in your attic or maybe around the perimeter of your basement, where the house rests on the foundation. What does this mean? Is it moldy? Wet? Why is the insulation black?

In fact, black insulation is the energy auditor’s best friend because it tells us where the problems are. In just a few minutes of looking around the attic, you can find the most serious air leaks from the house. Here’s why…

Continue reading

Cathedral Ceilings – Mold and Moisture – Problems and Solutions

Rotten roof deck

Disclaimer: while I think all the information presented here is accurate and scientifically valid, you are advised to consult a *professional before changing your home. This article covers just one component of your home. Your specific home may have conditions that override the comments contained herein.

*By professional, I mean an experienced building scientist, not your local carpenter or roofer or even a structural engineer or architect. While many of these people are artists in what they do, most have no training in building science or engineering and cannot be trusted to properly design a roof assembly. Likewise, you wouldn’t hire a building scientist to swing a hammer and build your roof!
Cathedral ceilings are very popular – they give rooms a feeling of openness and an added aesthetic dimension. At the same time, they are responsible for a variety of building problems and homeowner heartbreak. What causes these problems and how do you avoid them?

There are a variety of climate zones. The south-eastern United States is hot and humid, while the north east is cold. The mid-Atlantic states, where I live, is mixed – during the summer it is hot and humid, during the winter it is cold. The south west is mostly hot and dry and the northwest is moderate in temperature but very humid! Each of these climate zones has its own particular building details. However, all must follow the laws of physics.

Physics tells us that moisture moves from areas of high humidity to areas of low humidity. If it’s more humid outside, moisture wants to come in. And when it’s more humid inside, the moisture will move toward the outside. Simple!

Continue reading

If you saw smoke coming from the wall, you’d call the fire department and evacuate the house.

If you saw smoke coming from the wall, you’d call the fire department and evacuate the house. So why, when you see water dripping from the ceiling, do you put a bucket under it, and let it destroy your home just as surely as the fire would, just more slowly?

This is just a quick thought for the day. Water can be extremely damaging, but it seems so innocuous that people often ignore it until it destroys their home or their family’s health. Take every drip seriously – imagine that each drip is a puff of smoke coming from a hidden fire.

Got Mold? Part 3 – a flood doesn’t have to be the end of the world

By now, you’re probably terrified of water, and well you should be – it is a silent destroyer of homes. On the other hand, I don’t want anybody freaking out because they spilled a bucket or even a glass of water on the floor!

Mold doesn’t grow instantly. It needs time, water, and sometimes warmth. I’ve seen plenty of cases where people have had a serious flood in their homes – perhaps a toilet or sink flooded a bathroom, but these resulted in no mold. Why? Because the water was cleaned up quickly and everything was allowed to dry out.

The danger is when you let water or condensation get trapped somewhere. For example, I see this a lot – house-plants causing rotten wood, like shown above. There was a huge house plant sitting in a plastic pot. The pot didn’t leak, but periodically, somebody might spill a little water which would go under the pot and get trapped. Over time, it totally ruined the oak floor.

Trapped water is bad. Water left to evaporate is usually harmless.

Most of the mold and water damage I’ve seen occurs over a long period. Weeks, months or even years of neglect. So it usually isn’t a surprise when you find problems. However, like the proverbial slowly boiling frog, we often ignore a “little” condensation or a puddle of water. But, these are exactly the things that cause you to wake up one day and find that your window sash has rotted out.

A little moisture over a long period can cause serious damage.

Let’s look at a few scenarios and classify them as bad or not-so-bad.

Scenario 1:

Your toilet or sink overflows, but you catch it quickly. Maybe a couple buckets worth of water floods your bathroom.

First off, any time you have a water spill, the first thing to do is to clean up all the water (duh)! If you have a wet-use shop-vac, you can put it great use. Shop vacs do a wonderful job of cleaning up spills because they’ll suck the water off the floor and out of nooks and crannies. If you don’t, then use a sponge mop and soak up all the water.

When you’re done with the bulk of the cleanup, use an old towel to dry everything as well as you can.

Often, this simple cleanup will be enough if you catch the leak before it has a chance to really soak in. So beyond this, just run the bath fan for a few hours to flush out the moisture in the air or run a big floor fan in the doorway. 

All told, this type of “water event” can be pretty harmless. 

Scenario 1a:

You flood the bathroom with enough water that it drips out the ceiling or light fixtures in the floor below. 

This could mean trouble. In most homes, you have the finish flooring, with a wood sub-floor underneath. This sits on the floor joists. Underneath, the ceiling material, usually sheet-rock, is nailed or screwed to the underside of the joists. If the water flooded down to the floor below, that means that a substantial amount is likely in this space around the floor joists which you can’t get to in order to dry it out.

As in scenario 1, you want to immediately clean up the water above. Forget the floor below (yet) – stop the water above from coming down! If you clean up the water and get the bathroom drying out, that will help the water evaporate and allow all the building materials to dry out. Remember – water “wants” to move from wet to dry areas.

However, your work isn’t done yet. There’s a good chance that your sheet-rock will pull away from the nails/screws that hold it up. When it gets wet, sheet-rock will turn to mush. Don’t touch it or you may destroy it. You also run the risk of having the ceiling collapse on your head.

The best thing to do is clean up all the visible water from the bathroom and the floor below and then put dehumidifiers in both rooms. Let them run for a couple of days. You literally want to suck the moisture out of the building materials as fast as possible.

If you’re a professional and have good toys, you can use a moisture meter. I have a few of these. They let me scan behind walls and ceilings without having to take everything apart. There are two types – the pin type, which is generally more accurate but requires that you stick the probes into the material, and non-destructive, which works on the electrical properties of the material which change with water content.

The problem is, if you don’t have one of these meters, you really don’t know how much water remains in the ceiling cavity. If that water isn’t totally dried out quickly, you’ll probably have mold growing in there. You will be very unlikely to have wood rot however because the water will get soaked up and evaporate over time so the conditions for continued mold and related problems decreases over time.

The question is, if you do get a little mold in there, is that a problem?

Before I answer, if you have any doubts whatsoever about you or your own family’s sensitivities to mold, contact a professional. Without actually examining your home, there is no definitive information that anybody can give you. In other words, if you choose not to have a professional evaluate your problem and your house collapses or you die of mold allergies – don’t blame me!

There is a school of thought that as long as you get rid of the water let the mold grow in the first place, you don’t want to mess with it, especially if it’s safely trapped in the walls or ceiling.

What would I do? When I’ve had situations like this in my own home, usually after I’ve dried things out, I will cut a hole in the ceiling – maybe 16” square. Large enough to poke my head into and check things out. Sheet-rock is easy to patch, and you’re better safe than sorry. Though now that I’ve got those excellent moisture meters, if they indicate that it’s dry in there, I don’t worry about it.

Scenario 2: 

You’ve had a flood that you didn’t discover for a couple weeks.

This is bad news, really bad. I’ve seen homes totaled by this. Seriously.

This typically occurs when a pipe bursts in a vacation home. Or a rat chews through the water lines of your dishwasher or washing machine. The water pours out, gallons every minute, for the entire time. It’s horrible. Thousands of gallons flooding into every corner of the house, soaking into the carpets, up the walls, into every cavity.

In a situation like this, the only solution is to call in a water damage specialist. Hopefully your insurance will cover this, because it will cost thousands of dollars and take potentially weeks to dry out your home and determine if it’s habitable.

Here’s what they’ll do.

First, as in any of these situations, they’ll turn off the water to ensure that no more water enters. Next they’ll remove the “bulk water” so that it can’t cause further damage. This is the easy stuff.

Next, they’ll probably want to remove all the water soaked materials. This might include sofas, carpets, beds, anything that is wet and holding moisture. If they leave these giant wet sponges in the house, it will be extremely difficult to dry out the house.

After that, they’ll use industrial strength dehumidifiers and fans to dry out the air. The fans help to evaporate the water and the dehumidifiers suck the humidity out of the air. 

If you’re lucky, they’ll make measurements using meters like I mentioned above, and they’ll determine that the interstitial spaces (i.e. inside the walls and floors) are dry. However, with this type of flood, it is extremely likely that the insides of the walls and floors will be saturated with water. This can be extremely difficult/impossible to dry out without opening up the walls.

As you can see, this is really serious. If you encounter this type of scenario, don’t mess with it!

Got Mold? Part 2 – Crawlspaces and Moisture

Crawlspaces – they are some of the nastiest places around your home. Usually they’re filled with cobwebs and dust. They’re too low to move around in comfortably. And often, they’re filled with moisture, mold and wood-eating insects.

Because of this, most people avoid them. I had the misfortune of being the guy who spent every working day in these spaces until my knees and back deteriorated to the point that I couldn’t do it any more. So I’ve seen a lot of *yuck*. I’ve seen floors that were about to collapse. I’ve seen standing water. I’ve seen more rotting, dead mice than I ever wanted to. And I’ve seen mold. Boy, have I seen mold.

Unfortunately, the picture above is more typical than not. Most people’s crawlspaces are moist enough so support mold growth on the paper backing of the insulation between the floor joists. By the way, did anybody ever tell you that mold loves cellulose (i.e. paper)? So that insulation you put down there is a perfect place for mold to grow. Once it does, it basically eats the paper and your insulation falls down. Now you have a big, soggy piece of fiberglass sitting on the ground – mice love it, so they’ll use that as nesting material. It gets really nasty.

Mold 101

Remember what I wrote in earlier postings? Mold is everywhere and mold loves humidity. Give them proper conditions for growth and they WILL grow like crazy. And when they grow, they need to eat. Google “dry rot” and you can read more articles than you want about the topic. Here’s one.

Why Crawlspaces?

Most crawlspaces have been built incorrectly since the dawn of time. Or at least since builders started getting cheap and building crawlspaces instead of a real basement.

Let’s start with the worst type of crawlspace – the dirt floored crawlspace.

What is dirt? Well, technically, it’s basically a big sponge. Dig down a couple feet outside and what do you get? Damp soil. Damp means water. That water travels through the “sponge” and into your crawlspace. Then what? Well, physics dictates that water will move from damp spaces to less damp spaces until the two are at the same humidity level. So the moisture in the ground “wants” to evaporate and saturate the air in your crawlspace.

Unfortunately, since there’s an infinite amount of moisture in the ground, there is continuous supply of moisture moving from the ground into your crawlspace. This leads to the Sisyphean task of trying to dry out a crawlspace with a dirt floor. (You remember Sisyphus – he was the guy damned to roll a boulder up a hill for eternity and every time he made progress, the boulder rolled back to the bottom).

So what do you do? Most people will Google it, and go to the first link. They’ll then be confronted with a bunch of bad advice from idiots who don’t know physics, moisture dynamics, or the first thing about why and how problems arise.

Instead, use this search on the website. Joe and his crew are building scientists – they actually understand the problem. So don’t pay attention to what anybody else says on a discussion group, go straight to the source.

Since you’re still here reading, I’m assuming you looked at BuildingScience and decided it was too technical, so you want to hear about how to fix the problem in plain English.

So here you are, stuck with a damp crawlspace and you want a solution. You’ve tried a dehumidifier and ventilating the crawlspace, and all that happened was your electric bill went up $100. Maybe you got lucky and it dried out until the next rain, at which point you ended up with puddles but you were still out $100 and were no closer to a solution. Now what?

Ok – you have to do a little detective work. First off, if you’re getting puddles in your crawlspace, you’re either built on a natural spring, or the drainage around your home isn’t done right. Pray that it’s not a spring, because I can’t help you there. Sell your house and move, now….

Let’s assume that it’s a drainage problem. Walk around the outside of your house looking for drainage problems. For example:

That is the number one cause of water in the basement or crawlspace – the downspout isn’t attached or is dumping water right onto the foundation walls.

So the first thing you want to do is to make sure your gutters work properly and the downspouts drain at least 6’ away and downhill from your house. Don’t take shortcuts! You have to get the gutters properly draining away from your house.

If you’re serious about it, you’ll have the gutters tied to a drainage system going to a dry well far away from the house.

Why is this so important? Because, when it rains, your gutters are trying to dump thousands of gallons of water and if you dump that much water around your foundation, it’s going to come into your house, which will raise the humidity and lead to moldy conditions. Not just in your crawlspace, but maybe in your attic and everywhere else. Proper drainage is key.

The next bit of detective work requires that you get muddy and wet. I know, you don’t want to get yucky, but tough it out. It’s better than having your house collapse due to all the water and mold rotting out your crawlspace.

Go outside during a heavy rain and walk around the perimeter looking for puddles. Take pictures so you know every place things aren’t right. This might be caused by gutters overflowing or poor grading or local depressions in the soil. 

Then, go inside and look at the basement and crawlspace walls. Do you see any streaks on the wall or other signs of moisture?

Maybe you’ve got something like this? That’s usually not a good sign!

Just use your head! If you don’t want water in your basement/crawlspace, keep it away from your house to start with. Note every place that doesn’t look right. Every puddle outside. Every water streak inside.

You may have to have some landscaping done. The soil around your house must slope away from the foundation or the water will get in.

So this is all step one – keep the water out in the first place. For most people, properly grading the ground and fixing the gutters will do the trick. If that doesn’t work, come back and read my next post. I’ll talk more about this topic. Until then, go work on your gutters. Please, please, don’t do this:

If you do this, you may as well just put a hose in your crawlspace and turn on the faucet!

There’s No Such Thing as a Small Leak!

Writing these posts have reminded me of all the horrors I’ve seen in buildings and homes. Unfortunately, some have been in my own house! This is one of those (unfortunate) cases.

This all happened some years before I got into the building science business, so I didn’t know the warning signs to look for, and it cost me dearly!

Not long after I moved into my home, we started hearing loud “settling cracks” coming from our kitchen, which has an attached sunroom. For a long time, we didn’t think much of it. The house was built in 1957 and had gone through various renovations before we moved in, so we just attributed it to natural 

Then strange things started happening. A large crack appeared in one section of the wall and floor tiles in the sunroom were breaking. However, this time, we attributed it to poor installation. Contractors echoed this sentiment, so we let it go.

Finally, in the middle of winter, after a particularly loud *CRACK* coming from the kitchen, I went to explore. It was then I noticed a blackening on the wall behind the kitchen table. I thought “mold”, and went to explore. Like any guy, I poked at it with my finger. Unfortunately, my finger went right through the wall! This was the start of a long night…

As I continued to poke at the wall, I discovered that the entire short wall, on which the prefab sunroom was installed, was rotten. This must have been going on for years because almost all the 2×4 wall studs had turned to mud – completely rotten. Argh!

By the end of the night, I had removed most of the floor tiles and all the rotten wall parts and found pressure-treated lumber to support the sunroom. Frankly, I was surprised that the entire sunroom hadn’t fallen down – it was that bad.

So What Happened?

What I discovered during the deconstruction was that all the materials were wet. This included the exterior walls and the subfloor under the tiles, which by now had rotted out too.

The following day, after I’d warned my wife not to set foot in the sunroom and start getting bids on rebuilding the kitchen, I went outside and studied the stone wall on which the sunroom was built. I also looked from the inside to see if I could find the source of the water. In fact, it was quite easy to find – I could see daylight through the wall! Further inspection showed that the builders were depending on caulk to water-seal the structure. This is a common cause of leaks.

Sidebar – Rant about Caulk

Folks, caulk is never to be used, especially on the outside of a house, as the primary line of defense against water leaks. If you use caulk, it will eventually give way and lead to a leak. I guarantee this. No matter what any contractor, brother-in-law or best buddy tells you. Caulk should not be used this way.

Think about it. You’ve got two different materials – in my case, an aluminum sunroom sitting on a stone wall. The massive stone wall changes size very little as it warms and cools while the aluminum changes dimensions considerably. In technical terms, the “coefficient of linear expansion” of aluminum is high compared to that of sandstone. If you want numbers, it’s double. And caulk? That expands and contracts ten times as much as metal and stone!

What that means is that if you go from 0F in the winter, to 100F in the summer (higher if the sun is shining on it), over the 8ft length of the sunroom, the aluminum will expand between one and two millimeters more than the stone and the caulk wants to change length by about an inch. If this happens repeatedly, and you combine these forces with the shrinkage of the caulk over time, the result is a guaranteed leak.

So if you’re considering using caulk in this way – don’t do it. Fixing the damaged caused by that $3.49 tube of caulk will cost you tens of thousands of dollars. 

Back to the Leak…

What else did the builder do wrong? Well, they ignored a piece of information that any grade-schooler could tell you – water runs down hill and puddles on flat spots. Why do builders think that they can ignore the laws of physics?

In this case, they built the sunroom on a flat topped stone wall. So when it snowed or rained, the water would sit on the wall – the only water barrier being a little bead of caulk. Not to mention that SANDSTONE IS WATER PERMEABLE, so any water that sits on it can wick around the caulk and enter the house.

The solution is relatively simple. Slope the top surface so that water flows away from the house – yes folks, water runs down hill. Use this to your advantage.

There’s No Such Thing as a Small Leak

This leak, caused by poor design and improper use of caulk, went unnoticed for a decade until my sunroom almost fell down. I won’t tell you how much it cost to fix it right. But it was such a painful learning experience. In fact, I’m here writing this today largely because of what I learned. Unfortunately, one of the most important things I learned is that some builders ignore the science of building and instead just focus on cosmetics. Remember, you cannot win the fight against physics!

What other problems can arise due to “small” leaks? Well, have you ever had a slow drip somewhere that you didn’t fix? You know, one of those leaks that maybe you just put a bucket underneath so that it wouldn’t stain your carpet?

Well, if you did that, you risked having your house collapse. Maybe not all at once, but it starts with a slow drip. Who knows where the drip started. Perhaps it was running down from the roof, working its way down a rafter, dripping on the attic floor, migrating down a wall, puddling on the ceiling, then finally dripping on your floor.

Every area that is subject to repeated wetting like this might, over time, get moldy then get eaten by termites or mold-related products. I’ve seen support timbers that became so soft I could poke my finger through them. Do you want this holding up your house? What happens during the next big snowfall or wind storm that puts pressure on your home? Seriously – this is life threatening stuff!

So if you ever discover a “small” leak, don’t wait till next month, or next year to have it fixed. Immediately, try to find the source of the leak. If it’s a leaky pipe, shut off the water to that pipe and have it fixed. If it’s a leaky roof, get it fixed correctly. Whatever the case, you need to dry out all the building materials, preferably with fans and dehumidifiers, as soon as you can, and get a professional in there to fix it.

A note about mold: some people have sensitivities to mold, others don’t. If you have moldy conditions, you have to deal with the source of the water, or the mold will keep coming back. But whatever you do, if you have any concerns, call in a mold remediation specialist. I can’t stress this enough – a specialist! Not your buddy who does carpentry on the side. Probably not your builder. A specialist who knows how to safely get rid of the mold and prevent it from coming back.