06-05-2014, 09:29 AM #1
- Join Date
- Jun 2014
- Phippsburg Maine
A roof question for a Maine house
I have read with great interest your many articles regarding building science as my wife and I have planned the renovation of our home. Our house is a kit log home that has been a constant source of frustration for the last 11 years. We live in Maine and buying this house was a compromise that gave us access to the ocean as well as a great neighborhood. We live on a saltwater inlet called "The Basin" in an association where we are clearly the most modest home.
Our primary frustration with the house is the fact that it is cold and energy inefficient. The pine logs used in the structure are a manufactured type with a flat interior surface and uniform curvature on the exterior. While they do have a tongue and groove on the top and bottom, it is remarkable how much movement occurs with expansion and contraction in our harsh climate. At the joints between the logs there is actually only 3 1/2 inches of solid wood. As the house is now approximately 27 years old, energy loss is compounded by the age of the windows and doors. While we do have an oil fired burner with hot water baseboard heat, we rely on a wood stove as our primary heating source. We plan on adding an on-demand propane fired hot water heater for domestic hot water in the renovation.
We are fortunate in that we have a talented architect as our friend and neighbor. Given our financial constraints we have spent a great deal of time coming up with a design which we feel will maximize our renovation investment. Our goal is to 1) encapsulate the house with insulation to increase comfort and energy efficiency, 2) completely change the flow of the house to accommodate a formal entrance, new master bedroom and master bath and an open concept kitchen/living area. In doing so, we will completely change the aesthetic of the house from log home to traditional New England shingle style.
I am writing primarily to ask for your guidance in terms of the roof insulation. Currently, our roof consists of 3 inches of rigid foam on top of v-rustic with two by fours laid face down to create an airspace under the sheathing for roof venting. (Please see the photos and plans for our project at: https://plus.google.com/photos/10941...21875442185329 ) While we had originally planned to use closed-cell spray foam on both the walls and the roof, the cost was simply prohibitive. As an alternative, our architect has suggested using the Johns Manville 4” Nailboard panels as an alternative. While applying them to the walls appears to be a relatively straightforward process, the question as to whether or not to vent the roof has created significant debate. As you can see on the roof detail in the plans, our architect has suggested maintaining the roof vent and simply applying the insulated panels over the existing sheathing. Based on some of the articles which I read in your publication, I am inclined to consider a hot roof. While I'm still relatively new to the concept of determining the dewpoint within rigid foam insulation, I'm definitely ambivalent as to how to best proceed.
So in summary, I'm asking for your opinion on the following matters:
1) Whether to vent or not vent the roof?
2) In your opinion is the Johns Manville product best option for this application? I have recently seen another product, The RAY-COR Panel which appears to be faced on both sides with foil.
3) While I am a great believer in the use of Grace Ice and Water Shield which has been specified by our architect for the entire roof, our contractor is suggesting the use of Ice and Water on critical areas and using another product called “Sharkskin” for the balance of the roof. Are you familiar with this product and you feel this a reasonable substitute?
As I'm sure you can appreciate, this project represents a huge investment for us. As my wife and I approach our 60s it is our hope that we can achieve a level of comfort and security in our home without incurring unreasonable debt. Since I have some construction experience, albeit a bit rusty, we have negotiated with our contractor my doing all the demo, cleanup and grunt work to reduce costs.
Thank you in advance for your time and consideration and I look forward to any feedback you may offer.