My Beef With One-And-One-Half Story Houses

I've lived in a one-and-one-half story house in Minneapolis for the last six years, and I feel like I've earned the right to complain about them.  My main beef with them is insulation and ventilation; they're a pain in the butt and they're expensive to get right.


There are two primary ways to insulate a one-and-one-half story house: traditionally, or with a hot roof.

Hot Roof

Hot roofs are actually pretty simple.  A hot roof will have foam insulation sprayed against the roof decking, and won't have any ventilation.  If a closed-cell foam is used, it will act as a perfect vapor barrier, and will prevent any air leakage.  Simple.  I'm a big fan of this method, and I even did it at my own house.

The problem with spray foam is that it's hideously expensive, and the installers need to have access to the roof boards; that means the attic space needs to be gutted before the work can happen.  If you're doing a big remodel, great... otherwise, it's just not practical.

Traditional

The traditional way to insulate and ventilate a one-and-one-half story home is to insulate right up against the first floor ceiling, the knee walls, the vaulted roof sections, and again at the second floor ceiling.  The diagram below illustrates this nicely.

The cold spaces shown above are all supposed to be ventilated.  The ventilation will help to keep these spaces cool during the winter, which helps to reduce the potential for ice dams at the exterior and condensation in the attic.  The illustration below shows one way to do this.

In this illustration, soffit vents are installed at the eaves, baffles are installed between the lower and upper attic spaces, and gable end vents are installed.  There are other ways to achieve a similar venting strategy, such as using a continuous ridge vent at the top section instead of gable end vents, but the main idea remains the same.




The problem with traditional insulation is that it's very difficult to retrofit an existing installation.  Some homes have access to all three of the attic spaces, while others don't have access to any of the attic areas - and there is never access to the vaulted roof sections between these attic spaces.  To get at these areas, it often involves gutting the upper level.  Sure, more insulation can easily be added at the knee wall attic areas, but that's just a fraction of the total heat loss that's occurring here.




With traditional insulation, attic bypasses also need to be sealed... and these houses have a ton of them.  Perhaps the largest bypass is the one that occurs right below the knee wall, which is illustrated below.  This area needs to be sealed off to prevent warm air from leaking in to the unheated attic areas.



What this all boils down to: if you're buying a one-and-one-half story home that hasn't been properly insulated and ventilated, you'll probably have to gut your upper level if you want to correct it.


Oh, and another thing... these homes will often have just one supply and one return register from the furnace at the upper level; combine that with poor insulation, and you have a cool space in the winter and a hot space in the summer.


Oh, and another thing... they're prone to ice dams.


Oh, and another thing... no, that's enough whining for today.



Reuben Saltzman, Structure Tech Home Inspections - Email - Home Inspector Twin Cities

    
Note: The diagrams in this blog entry came from www.nrcan.gc.ca.  I marked up the diagrams to help illustrate my points.

Hot Roofs: A Misnomer

Reuben's Attic

While most attic spaces in Minnesota are insulated with fiberglass or cellulose insulation, there is a relatively new product that provides superior performance:  spray foam.  Spray foam is the best way to insulate homes, especially old one-and-a-half story homes, and I'm such a firm believer in this that I had it done on my own home a couple years ago.  Spray foamed roofs are commonly referred to as 'hot roofs'.


Why are they called 'hot roofs?' Traditional attic spaces have insulated floors and are ventilated.  Air comes in at the soffits and leaves at the top of the roof, creating a cold attic space.    This helps to prevent ice dams, keeps the roof cooler in the summer which helps to prolong the life of the shingles, and may help to prevent the accumulation of condensation.  Spray foamed attics have foam applied directly to the roof sheathing, and the attic space isn't ventilated.  The lack of ventilation is why we call them hot roofs.


Are they really hot? No.  Studies have shown that color differences in shingles will actually have a larger impact on the temperature of roofs than the difference between a ventilated and a spray-foamed roof.  A 'hot' roof will typically only be a couple degrees warmer than a ventilated roof.


What are the benefits? Spray foam has a higher insulating value (R-Value) than anything else.  Sprayed Polyurethane foam insulation has an R-Value of 6.8 per inch, while fiberglass batt insulation is about half that.  Foam insulation also makes for a perfect seal - no gaps, no air leakage, no attic bypasses.  If ductwork is located in the attic space it won't need to be insulated, elimating energy loss here, which can account for up to 10% of total energy loss.  One more benefit that I personally love is having a warm attic area for extra storage!  Note: My old house is designed in such a manner as to support extra storage in the attic, but most newer homes are not.  This might be another blog topic some day.


What are the downsides? The only one I know of is cost.  Spray foam insulation will typically cost thousands more than fiberglass or cellulose.  I paid about $3700 to have my own attic spray-foamed with polyurethane, but I could have spent about a third of that to have fiberglass installed, along with proper vents.


Will spray foam void my shingle warranty? Probably not.  Most of the major manufacturers of shingles still warrant their products when used with a spray-foamed attic.   Owens Corning, however, does not.

If spray foam is so great, why isn't it used on walls? It is.   I have a friend who insulated the walls in his home when he built it in 1981.  Spray foam is also used at the rim joist in almost every new construction home that I inspect.

Additional Information - technical, dry reads.
Spray-in-Place Polyurethane Foam Insulation Opion Paper, by Craig DeWitt, Ph.D., PE
Vented and Sealed Attics in Hot Climates, by Joseph W. Lstiburek, PE


Reuben Saltzman, Structure Tech Home Inspections - Email - Minneapolis Home Inspections

Reasons To Insulate Your Minnesota Home

With the cold weather officially here, it’s a good time to talk about insulation.  This is such a huge topic that I hardly know where to start!  There are so many different aspects to insulation that this will have to take up several blogs.  Today I’ll talk about why it’s important to have a well-insulated home.


Perhaps the most important reason to have a well-insulated home is to reduce greenhouse gas emissions.  While a recent survey conducted by Owens-Corning revealed that most Americans believe transportation and industry to be the largest contributors of greenhouse gas emissions, in truth the largest contributor is buildings!  Buildings use 40% of our energy, according to the U.S. Department of Energy.  The number is even higher in Minnesota - 60 to 80 percent! The most cost effective way to reduce greenhouse gas emissions is to better insulate buildings.  Yes, this is even better than driving a hybrid vehicle, but it's certainly not as hip.


The most obvious reason to better insulate your home is to reduce your heating and cooling bills – especially here in Minnesota.  Adding insulation to attic spaces is often a project that even unskilled homeowners can tackle, and it doesn’t cost a lot of money. Homeowners will typically see a payback in five to ten years. Adding insulation to poorly insulated walls is also a good thing to do and will surely help to save on heating and cooling costs, but this not as cost effective as adding insulation to an open attic area, as this will often require a professional to blow insulation in to the walls.


Arguably the most important reason to better insulate your home is to make it more comfortable. Even if a thermostat says it’s 70 degrees inside the home, poorly insulated walls will make a room feel much colder as the heat from your body radiates out to the relatively cold walls. In older houses with uneven heat, you may even have parts of the house that never warm up enough. I can tell you from experience that insulation makes an incredible difference in the comfort of a home. I live in a one-and-a-half story home with a finished upper level that used to be so cold in the winter that I couldn’t even use it. After re-insulating the upper level last year, I no longer need to heat the upper level! Enough heat rises up from the rest of the house to keep the upper floor so warm that I can shut off all the heat registers and it’s still comfortable.


There are many more reasons to properly insulate your home, but I’ll just mention one more that you’re surely aware of if you live in Minnesota; ice dams. While ice dams are a large subject on their own, suffice to say that lack of insulation can lead to large accumulations of ice at the edges of roofs that cause leaks in the home and destroy gutters.

In my next blog I'll talk about how to determine whether more insulation is necessary, and what critical steps need to be taken before adding insulation. Hint: the photos throughout this blog all show homes with major room for improvement!

Reuben Saltzman, Structure Tech Home Inspections - Email - Minneapolis Home Inspections


Related Post: Photos Of Problems With Explanations