Att_08_Enclosure_Assessment_Report_10-15-2019.pdf

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Yellowstone National Park – Laurel Dormitory Building Enclosure Assessment Report

Prepared For A&E Architects

Yellowstone National Park, Wyoming

October 15, 2021

Table of Contents

1 Background

2 Assessment Methods

3 Assessment of Current Conditions

4 Discussion & Recommendations

4.1 Crawlspace

4.2 Above Grade Walls

4.3 Porches and Awnings

4.4 Attic

4.5 Roof

1 Background

Morrison Hershfield (MH) was previously retained by A&E in August/September of 2019 to assist in conducting a conditions assessment report for the Laurel Dormitory located in

Yellowstone National Park. The objective of the investigation was to attempt to determine the cause of the reported issues and work toward a resolution plan. MH provided a report to

A&E with the findings and recommendations for resolution on October 04, 2019. After limited remediation to the building, mainly focused on the crawlspace, a follow-up investigation was requested after two years of continued operation in order to inform a

Request for Proposal for complete rehabilitation of the building.

2 Assessment Methods

The follow-up on-site investigation was completed on June 8-9, 2021 by Jack Pearson of

Morrison Hershfield. The fieldwork included a visual and infrared review of exterior and interior elements of the Laurel Dormitory including the crawlspace, occupied levels, vertical walls, attic, and roofs. Invasive investigation of interior walls was performed to confirm anomalies noted in infrared thermography. Climatic monitoring of the crawlspace with data loggers (recording temperature and relative humidity) was performed by placing monitors at multiple exterior, interior, and crawlspace locations.

3 Assessment of Current Conditions

Current conditions were evaluated from MH’s follow-up field assessment and understanding of remediation performed after our initial review. Generally speaking, MH observed the same issues that were noted two years ago which had resulted in further deterioration of building materials. MH believes that the building would be in worse condition if it had not been partially remediated. That remediation included a new mechanical system in the crawlspace and spray foam insulation installed on the underside of the floor above the crawlspace. MH observed that the motor for the crawlspace mechanical system was running but that the fans were not operating because fan belts had been removed. While the ventilation system was not actively providing ventilation to the space, the unblocked vents around the perimeter of the crawlspace appeared to be providing natural ventilation that had a positive impact on the condition of the crawlspace (decreased temperature, relative humidity, and negative impact on building materials). The spray foam insulation on the underside of the first floor was limiting crawlspace air and moisture vapor from reaching the floor above. However, MEP penetrations through the floor had not been consistently sealed by the sprayfoam and we observed issues in walls above including conditions conducive to microbial growth. See the previous conditions assessment report dated October, 4th 2019 for detailed documentation of all noted issues with the building enclosure.

Figure 1. Overall image of the south elevation

Figure 2. Overall image of the south elevation

Figure 3. Overall image of the north elevation

Figure 4. Overall image of the north elevation

Figure 5. Overall image of the low-slope and mansard roof

Figure 6. Louver integrated with new mechanical system in the crawlspace

Figure 7. Crawlspace with spray foam insulation on the ceiling separating it from the first floor

Figure 8. Crawlspace with spray foam insulation on the ceiling separating it from the first floor

Figure 9. Infrared image showing air leakage in stud cavity at an interior wall on the first floor

Figure 10. Corresponding visible light image to Figure 9

Figure 11. Infrared image showing air leakage in stud cavity at an interior wall on the first floor

Figure 12. Corresponding visible light image to Figure

Figure 13. Degraded wall materials from moisture vapor intrusion from crawlspace below

Figure 14. Location in Figure 13 with paint removed and what appeared to be microbial growth previously identified by an industrial hygienist

Figure 15. Location where air leakage was noted on the IR camera on the first floor

Figure 16. Location in Figure 15 with paint removed identified by an industrial hygienist

Figure 17. Invasive opening at the location in Figure 15.

Figure 18. Stud cavity from Figure 17 with an unsealed penetration through the floor separating the crawlspace and the first floor

Figure 19. Location where air leakage was noted with IR camera on the first floor and what appeared to be microbial growth previously identified by an industrial hygienist

Figure 20. Invasive opening at the location in Figure 19 identified by an industrial hygienist between the paint and drywall

Figure 21. Invasive opening at the location in Figure 19 identified by an industrial hygienist between the drywall and stud cavity

Figure 22. Stud cavity from Figure 21 with an unsealed penetration through the floor separating the crawlspace and the first floor

4 Discussion & Recommendations

Based on the review of the exterior and interior conditions of the Laurel Dorm building enclosure and our understanding of the design intent, MH has prepared recommendations for building enclosure remediation and consolidated them into the discussion below. A&E requested that we provide cost estimating data with our recommendations. As we do not typically provide cost data, our information is limited, but we included anything we were able to gather in the time available.

4.1 Crawlspace

In summary, MH believes that the issues within the crawlspace, its interactions with the building above, and degradation of building materials are due to multiple sources of heat and moisture intrusion from below and above grade. The significant moisture load into the crawlspace is damaging the building in multiple ways. Noted negative impacts included structural damage from wetting and drying cycles causing rot, corrosion of fasteners and plumbing, microbial growth (noted during our investigation and previously confirmed by an industrial hygienist) occurring at and above the floor assembly, and conditions conducive to condensation. The remedial work performed within the crawlspace after the last investigation improved conditions and reduced continued degradation but did not completely stop the issues from progressing.

In order to address the noted issues, MH recommends a multifaceted approach to minimize the buildup of moisture in the space and provide a means of tempering the space to minimize risks.

1. To reduce the moisture ingress from below grade, MH recommends the installation of a vapor retarder over the entire floor area of the crawlspace (recommend Stego

Wrap 20 mil vapor retarder with manufacturer’s tape, accessories, and terminations including a termination bar on the foundation wall). Ideally, this should be installed over an even, continuous substrate. Ballast is recommended to be placed on top of the vapor retarder to hold it in place and protect it from damage during installation and maintenance access. The vapor retarder should be terminated to the perimeter of the space as well as any penetrations in the floor. We recommend providing a gas exhaust system similar to radon exhaust system to prevent buildup of gases from beneath the vapor retarder. The crawlspace should be secured to prevent unnecessary foot traffic that could damage the vapor retarder.

2. To address the moisture sources at the foundation wall, MH recommends two possible approaches. The best performing option is to install a waterproof membrane on the foundation walls as far down as possible with a protective drain mat and drain rock (French drain) to the depth of waterproofing. This option would require all cracks and bug holes in the foundation to be filled, the wall waterproofed, and subsequently be covered with soil or cladding. The recommended waterproofing system is GCP Bituthene 3000/4000 (self-adhered) or Soprema

Colphene Flam 180 FR GR (torch-applied). MH recommends considering installation method (self-adhered vs torch-on) as the Contractor may prefer or do better with one method over the other based on the season of installation (torch-applied is more tolerant of low ambient temperatures). The Bituthene system typically costs $1.50-$2.00 per square foot (sf) for materials and is installed around

$6.00 per sf.

If the design intent is for the foundation to remain exposed, the second approach would consist of filling all cracks in the foundation wall and installing a water-resistant coating on the exterior. The recommended water-resistant product would be GE SilShield Optic, which is a clear silicone, air and water barrier that is not completely invisible but adds only minimal visible luster. Because it is a barrier system, this would be a maintenance item that would need periodic review to ensure long-term performance.

3. MH recommends the addition of free-draining gravel and plumbed perimeter drainage for the building perimeter. The most effective drainage would be located at the bottom of the foundation wall, or as far down as possible with the limitations on allowed excavation. Landscaping and grading should be designed to drain water away from the building.

4. Liquid water intrusion should be further mitigated by providing an interface between the air and water barrier on the building walls and the foundation with a kick-out flashing at the base of the shingle cladding. This will provide continuity and drainage of the wall system out and away from the foundation.

5. MH recommends that the new mechanical system that was installed be repaired to provide an active ventilation system. Consider securing the mechanical system against future tampering.

6. The closed-cell spray foam that was added performed as intended to compartmentalize the crawlspace and cut off its interaction with the building above, except at penetrations that were not well sealed. MH recommends added spray foam around all penetrations through the floor to provide an airtight seal. MH also recommends pouring a concrete slab on the first floor and installing smoke seals at all penetrations to provide greater separation from the crawl space.

7. To confirm the effectiveness of any remedial measures taken, MH recommends permanent hygrothermal conditions monitoring in the crawlspace and the floors above to confirm the approaches are effective and to identify issues if and when they occur.

4.2 Above Grade Walls

MH believes that the deterioration and reported microbial growth issues occurring in the building walls are a combination of the crawlspace issues discussed previously and further moisture intrusion from the enclosure not being air or watertight.

In order to address these issues, MH understands that the project team plans to fully strip the building walls down to the studs and install retrofit historical storm windows over the restored existing windows. MH recommends the following components for the exterior wall assembly:

1. From the interior, replace all batt insulation in exterior wall cavities with new mineral fiber insulation and an interior vapor retarder. Our preference would be to install

Sprayfoam in the cavities, but we understand that the project team would like to avoid the encapsulation of MEP in wall cavities in case of future renovations.

2. From the exterior, remove all shingles and existing weather-resistive barrier (WRB).

Sheathing repairs or upgrades should be provided as necessary for structural integrity. MH recommends confirming with a structural engineer.

3. MH recommends a continuous, self-adhered or fluid-applied, vapor-permeable air and water barrier (AWB) system with associated accessory components. A single source (manufacturer) should be maintained for all system components and accessories. The AWB system should interface all adjacent assemblies (including porch roofs), penetrations, and fenestrations with continuous air and watertight detailing. For a self-adhered product, MH recommends the 3M Air Barrier 3015 system. For a fluid-applied system, we recommend GCP Perm-a-Barrier VPL50 .

The Perm-a-Barrier system typically costs $0.85 per sf for materials and is installed between $3.00-$6.00 per sf. It is important to consider the application method (fluid-applied vs self-adhered) as each has different benefits/challenges. Fluid-applied systems excel at penetrations, openings, and detailing while self-adhered sheet systems excel in the field of the walls. Installing fluid-applied systems can be challenging in alpine winter conditions and this would likely require tenting and heating to be able to work if installing in the winter. The 3M 3015 system is unique in its ability to be installed down to 0 °F without the use of a primer.

4. MH recommends replacing the existing windows but understands that the intent is to restore them and install storm windows over top. The AWB system should interface with both window systems with continuous air and watertight detailing. This detailing should be determined once the design of the restored windows and storm windows is determined.

5. Exterior mineral fiber should be installed over the AWB to the depth that will be created between the sheathing and the storm windows (expected to be approximately 3” to 4”). At a minimum, we recommend 2” exterior mineral fiber insulation.

6. The new cladding (assumed to be shingles to match the existing) should be installed on a thermally broken girt or clip system such as SMARTci Green Girt, Cascadia

Clip, or Knight Wall MFI Rainscreen Attachment.

7. MH recommends kick-out flashing at all window heads and floor lines to direct water out of the wall system.

4.3 Porches and Awnings

MH recommends that each porch be stripped, reroofed, and integrated with the new AWB and cladding systems on the building. There are a variety of options for re-roofing the awnings and the desired aesthetic may drive recommendations for the performance aspects including but not limited to standing seam metal roofing, single ply membrane, or shingles. MH recommends the space beneath the north porch be cut off from the main crawlspace completely and made fully open to the exterior (we recommend against sheathing and cladding the structure of the porch).

If the space under the porch is to remain enclosed, MH recommends active ventilation and vapor control similar to the recommendations for the main crawlspace.

4.4 Attic

Attic issues appeared to have a relatively minimal contribution to bulk water and moisture intrusion and resultant whole building issues but should still be addressed.

1. MH recommends installing intentional venting in the attic designed per industry standards. Venting should include adequate pest occlusion screens as we understand rodents have been problematic in the attic. A key point of access was noted to be the construction of the roof access hatch, which could easily be reconstructed to prevent access.

2. Remove all existing insulation and vapor barrier products in the attic floor (2nd floor ceiling) assembly, temporarily remove the existing catwalk, and install a medium-density, closed-cell spray foam insulation (recommend Icynene Proseal, Johns

Manville Corebond, Bayseal CCX, or similar) at a minimum thickness of 3” over the entire second-floor ceiling surface to provide a continuous air barrier. Ensure all wall penetrations and interfaces to the mansard roof and building walls are detailed to prevent air and water penetration and pest intrusion.

3. If the project team prefers to avoid the use of spray foam insulation, MH recommends a spray applied, fluid air and water barrier on the attic side of the 2nd floor ceiling with penetrations detailed and sealed. Mineral fiber insulation could then be installed over the air and vapor barrier.

4.5 Roof

Roof issues appeared to have a relatively minimal contribution to bulk water and moisture intrusion and resultant whole building issues but should still be addressed.

1. MH understands the design intent is to remove and rebuild the mansard roof with cedar shingles. Given the fact that wood shingles will be installed we recommend using two layers of fully adhered GCP Ice and Water Shield HT (IWS) underlayment with a 50% overlap and staggered seams. The double-layer system will help to prolong the life of the roof which could be limited by the wood shingles absorbing water. Cedar shingles should be dipped in an appropriate coating to reduce moisture absorption and improve fire resistance. If any copper flashing will be used, GCP Ultra underlayment must be installed beneath it. The IWS HT system typically costs between $0.80-$1.20 per sf for materials, the Ultra system costs between $1.40-

$1.80 per sf, and installation varies significantly based on the local market and building type. If a Class A fire rated roof is desired, MH recommends an additional layer of fire-resistant underlayment over the IWS such as Eco Chief Solarhide or similar.

2. MH recommends insulating the underside of the mansard roof to reduce the risk of ice dams forming due to heat trapped beneath the roof. Given that the mansard roofs are fully exterior, this could be mineral fiber concealed with a soffit.

3. MH recommends that the low-slope roof be reroofed and re-sloped to improve drainage. For the best performance and lowest risk, MH recommends a torch-applied

2-ply SBS system such as Soprema Sopralene Flam 180 FR GR. If the appearance of this system is not acceptable, MH recommends a fully adhered single-ply PVC system such as Soprema Sentienl P150 (we expect grey would be preferred). If the appearance of the PVC is also not acceptable, a new EPDM system could be used.

Note that EPDM systems have a higher long-term risk of glued seams failing as opposed to heat-welded or torch-applied systems.

4. MH recommends including polyisocyanurate rigid insulation in the low-slope roof assembly to mitigate the impact of the sun and night sky on temperature fluctuations in the attic space. We believe this will improve the thermal performance and energy efficiency of the occupied space below. If insulation is included, a fully-adhered vapor retarder would be recommended beneath the insulation. The vapor retarder should be sourced from the same manufacturer as the roof membrane.

5. The interface between the low-slope and mansard roof will require careful detailing.

MH recommends that the interface be detailed with a PMMA fluid-applied product that is compatible with and adheres to Grace IWS HT and is sourced from the same manufacturer as the 2-ply SBS or single-ply PVC system for the low-slope roof. If the

PMMA cannot be sourced from the same manufacturer as the low-sloped roof system, MH recommends Soprema Alsan RS or Siplast Terapro if either can be confirmed to be compatible with and adhere to the chosen low-sloped roof system.

Please let us know if there are any questions or wish for further discussion. We are available to perform additional consultation in developing more detailed recommendations and strategies for the project as needed.

Thank you, Kelly Sabrowsky Jack Pearson, CBST

Building Science Consultant Principal, Building Science Consultant

Morrison Hershfield - Minneapolis Morrison Hershfield - Mountain

U.S. Buildings Consultation Group U.S. Buildings Consultation Group