Reuben's Home Inspection Blog

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

ReubensBeefI'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.

HotRoof

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.

Insulation Outline

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.

Ventilation Diagram

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 houses 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.


Attic Bypass under knee wall

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

Oh, and another thing... these houses 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

        

Comment balloon 8 commentsReuben Saltzman • May 11 2010 05:59AM

Comments

"...you have a cool space in the winter and a hot space in the summer." It sounds like in our home...

Posted by Catherine "Cathy" Chaudemanche- Edison, NJ, Full Time, Informed and Involved- Results Driven (Metuchen Keller Williams Elite Realty / Middlesex County, NJ) about 8 years ago

Catherine - how's your insulation?

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) about 8 years ago

Interesting Rueben.  I've never heard the term 1 1/2 story homes before.

Posted by Gabe Sanders, Stuart Florida Real Estate (Real Estate of Florida specializing in Martin County Residential Homes, Condos and Land Sales) about 8 years ago

This is exactly what I was discussing today with a homeowner. One point is your last illustration. The problem there is the insulation is usually not extended far enough into the warm area to create the desired thermal resistance. I have seen this through the IR camera numerous times. As long as the insulation is placed fully under the wall ending at the red line or even  a little beyond, there should not be a problem.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) about 8 years ago

Gabe - do you call them something else down in Florida, or do you just not have any?

James - as long as the insulation gets pushed far back enough there won't be a lot of heat loss, but moisture will still pass through that space.  No vapor barrier.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) about 8 years ago

Hot in the summer, cold in the winter, just like my home. Some day I'll remodel and fix it.

Posted by Dennis Chamberlain, Eastern WA Home Inspections (Eastern WA Home Inspections, LLC) about 8 years ago

Reuben, I shared a room like the one above with my brother til college!  It was always hot and cold!  But especially hot!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 8 years ago

Dennis - let me know how it turns out.

Jay - I didn't even use my upper level as living space until I remodeled it, because it was that uncomfortable.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) about 8 years ago

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