https://www.roofingcontractor.com/rss/2772 en-us gottliebb@enr.com (Bryan Gottlieb) http://www.roofingcontractor.com/articles/98689 Mon, 11 Sep 2023 09:23:29 -0400 https://www.roofingcontractor.com/articles/98689-how-inland-coatings-averted-irrelevance The work completed on a metal roof by R/J Group was quickly be put to the test as Hurricane Ian blew through only two weeks after completion.

]]> http://www.roofingcontractor.com/articles/98348 Wed, 07 Jun 2023 08:00:00 -0400 https://www.roofingcontractor.com/articles/98348-case-study-hurricane-ian-puts-new-roof-to-the-test gottliebb@enr.com (Bryan Gottlieb) The Kia Forum, outside of Los Angeles, was under pressure to have its existing rooftop logo removed and replaced. Contractor Centimark, using GAF products, got the job done on time. Learn how in this GAF case study.

]]> http://www.roofingcontractor.com/articles/98072 Mon, 20 Mar 2023 16:57:27 -0400 https://www.roofingcontractor.com/articles/98072-under-pressure-kia-forum-and-working-against-the-clock Thanks to polyurethane foam and Polyglass silicone coating, this 1-million-square-foot warehouse in Texas took on the brunt of an EF2 tornado.

]]> http://www.roofingcontractor.com/articles/97956 Mon, 20 Feb 2023 09:00:00 -0500 https://www.roofingcontractor.com/articles/97956-case-study-foam-roof-minimizes-tornado-damage-at-texas-warehouse Parallel Products is a leader in the sustainability industry naturally turned to upgrading its operations with solar roofing to reduce energy consumption.

]]> http://www.roofingcontractor.com/articles/97851 Fri, 20 Jan 2023 09:00:00 -0500 https://www.roofingcontractor.com/articles/97851-case-study-parallel-products-recycling-facility S5-Parallel-Products-Solar-1.jpeg Parallel Products, a recycling facility in Massachusetts, added solar PV to its metal roof, decreasing its carbon footprint and ultimately contributing power back to the grid. Photo: S-5! S5-Parallel-Products-Solar-2.jpeg.jpg Parallel Products of New England decided the best way for it to offset its electrical usage was to add solar. This new facility has increased solar capacity by 1.9 megawatts, part of its greater 4 megawatt solar initiative on campus. Photo: S-5! S5-Parallel-Products-Solar-3.jpeg.jpg The company’s main goal was to offset its carbon footprint since PPNE utilizes heavy machinery and equipment that consume an enormous amount of power. Photo: S-5! This state-of-the-art 6,000-square-foot LEED Platinum Certified residence is built solely with sustainability, energy efficiency and comfort in mind.

]]> http://www.roofingcontractor.com/articles/97642 Mon, 14 Nov 2022 09:00:00 -0500 https://www.roofingcontractor.com/articles/97642-case-study-the-net-zero-home-of-new-jersey Net-Zero-Home-NJ.jpg The Net Zero Home is a sprawling, state-of-the-art 6,000-square-foot LEED Platinum Certified residence built solely with sustainability, energy efficiency and comfort in mind. Photos: S-5! DJI_0031-min.jpg A PVKIT® direct-attach™ rail-less, solar mounting solution secured 80 LG high-efficiency solar panels in place on the metal roof. DJI_0892.jpg The home features an Englert A1500 snap-lock architectural metal roof and a 31-plus kilowatt PV solar system on its south-facing roof. DJI_0098-min.jpg The metal roof panels, made from 25% recycled material, are environmentally friendly and are LEED and ENERGY STAR®  compliant.  DJI_0947-min.jpg Along with the solar roof, the home features nine Tesla Powerwall® storage batteries (7.6 kilowatts each) as a supplemental power source. Using McElroy Metal roofing and wall panels, this storage facility became the brand's "flagship self-storage facility" thanks to its aesthetics.

]]> http://www.roofingcontractor.com/articles/97551 Wed, 19 Oct 2022 15:50:18 -0400 https://www.roofingcontractor.com/articles/97551-case-study-california-self-storage-gets-desired-aesthetic-with-mcelroy-metals-metal-roofing-wall-panels BroadStreetStorage1.jpg Phase 1 of building the Broad Street Self-Storage facility accounted for 59,430 square feet and included metal panels from McElroy Metal for the roofing, end walls and side walls. Photos: McElroy Metal. BroadStreetStorage2.jpg “It was important to the owners, who live in the community, to erect a self-storage facility that was functional and enhanced the aesthetics of the San Luis Obispo community,” says Raul Gonzales, project manager for MakoRabco Steel of Carlsbad, Calif. Challenges created by weather and the pandemic meant this project had to begin in January 2021 and be completed in a year, all while prioritizing energy efficiency. 

]]> http://www.roofingcontractor.com/articles/97370 Fri, 26 Aug 2022 09:00:00 -0400 https://www.roofingcontractor.com/articles/97370-case-study-vail-mountain-luxury-condos large-Vail Mountain View.jpg The luxury, multi-family Vail Mountain View Condos include nine residences and six penthouses that range in price from $7.4 million to $9.6 million and are designed for energy efficiency, meeting industry-leading sustainability standards. Photos courtesy of Atlas Roofing Corp. Vail Mountain View12.png Atlas ACFoam CrossVent™ was selected as a critical part of the roof system for the performance benefits of combining a cross-ventilating air space, nailable roof substrate, and thermally efficient continuous insulation. large-Vail Mountain View15.jpg “ACFoam, and especially ACFoam CrossVent, are our go-to products and Atlas is one of the only manufacturers we can depend on to get us their product when we need it,” said Jeff Johnston, owner of The Roofing Company. “We needed a solution that not only met an R-value of 20 on the roof but also provided a fully continuous insulation solution.” large-Vail Mountain View4.jpg As the crew members battled ice and snow during the extreme weather conditions, the team continued forward, even when it meant a total of 280 hours of shoveling snow from the roof. Vail Mountain View6.png The roof project using ACFoam CrossVent provides the insulation and ventilation needed to maximize energy efficiency inside the building, as well as reducing snow and ice buildup on the roofs. Petrini Custom Builders focused on creating a high-performance residential home, which included elevating design and performance using Atlas Roofing EnergyShield.

]]> http://www.roofingcontractor.com/articles/97278 Tue, 02 Aug 2022 08:00:00 -0400 https://www.roofingcontractor.com/articles/97278-case-study-atlas-energyshield-enhances-energy-efficiency-and-comfort-of-austin-residence Barton Hills3.jpeg With the help of Atlas EnergyShield, the vertical walls reach an R-value of 27.1 and the roof achieves an R-value of 38.1 for this home in Austin, Texas. Photos courtesy of Atlas Roofing Corp. Barton Hills Residence_11.jpg “Before we installed the siding and just had the EnergyShield exposed, you could feel the heat radiating off it. So, to see and feel the heat radiating off the insulation demonstrated so much of the effectiveness of the product because we knew it wasn’t going into the home," said Petrini Custom Builders President Tom Petrini. Barton Hills Residence_15.JPG In February 2021, Austin experienced a historical winter weather event that resulted in failed power grids, burst water pipes, property damage, and impacted travel in the area. In contrast, the Barton Hills residence with EnergyShield continuous wall insulation already installed – yet no siding at the time – did not experience frozen or burst pipes. When cedar shingles proved to be unfeasible for a historic structure in New York, roofing contractors turned to a CertainTeed shingle to match the site's harmony with nature.

]]> http://www.roofingcontractor.com/articles/96989 Fri, 13 May 2022 09:00:00 -0400 https://www.roofingcontractor.com/articles/96989-case-study-high-performance-roofing-product-benefits-restoration-of-19th-century-structure Camp Santanoni(57) At 16,500 square feet of roof area — not to mention seven chimneys, 38 valleys, and several dormers that required repair — replacing the roof of the Great Camp Santanoni main lodge was no small undertaking. Photo Credit: Jim Hamel & Titan Roofing. Atlas General Contractors in Illinois turned to Atlas Roofing products to help reroof and improve ventilation for a century-old church.

]]> http://www.roofingcontractor.com/articles/96906 Mon, 18 Apr 2022 09:00:00 -0400 https://www.roofingcontractor.com/articles/96906-case-study-atlas-roofing-polyiso-shingles-enhance-churchs-ventilation-durability-and-aesthetic Atlas Roofing Church Case Study_1 After installing approximately 162 squares of shingles, and cross ventilated polyiso roof insulation, the church not only had a stronger roof, but it also had an R-value of 30, providing more efficiency for the building and increased comfort for the congregation. Photos courtesy of Atlas Roofing. Atlas Roofing Church Case Study_2 When a storm damaged the church’s cathedral roof with high winds, the organization reached out to Gary Paris at  Atlas General Contractors, a general contracting services company not affiliated with Atlas Roofing Corporation. Atlas Roofing Church Case Study_3 Gary Paris at  Atlas General Contractors and his team found the installation of ACFoam CrossVent to be a straightforward and manageable process. Atlas Roofing Church Case Study_4 ACFoam CrossVent is a non-structural composite insulation that consists of ACFoam®-II or ACFoam®-III polyiso insulation board and APA/TECO rated OSB or CDX plywood, separated with and bonded to five individual 1-inch, 1.5-inch or 2-inch vent spacer strips. Atlas Roofing Church Case Study_5 Atlas General Contractors installed the Pinnacle Pristine high performance roof shingles Copper Canyon. Atlas Roofing Church Case Study_6 The shingles feature comprehensive warranty coverage against manufacturing defects, unsightly black streaks caused by algae, and damage from high winds. With help from S-5! products, SunGreen Systems Inc. installed a solar and energy system housing a 772-kilowatt photovoltaic array and 14 Tesla Powerpacks.

]]> http://www.roofingcontractor.com/articles/96905 Fri, 15 Apr 2022 12:00:00 -0400 https://www.roofingcontractor.com/articles/96905-case-study-californias-largest-commercial-solar-energy-storage-system 8606 Live Oak Ave., Fontana (1b) The Solar Atmospheres facility includes two roofs and carports that house a 772-kW PV solar system of 1,494 rooftop solar modules, making it California's largest commercial solar + energy storage system. Photos courtesy of S-5! 8606 Live Oak Ave., Fontana (14) SunGreen Systems installed solar on every possible area of the roof, built an addition to the southern building for more roof space and installed two, cantilevered carports along the property line to provide additional hosting of solar arrays. 8606 Live Oak Ave., Fontana (7) The facility's battery system is composed of 14 Tesla Powerpacks at 1,561-kW/3,122-kWh. A Texas roofing contractor relies on the protection that Owens Corning's Duration shingles offer to battle extreme weather in the Houston market.

]]> http://www.roofingcontractor.com/articles/96784 Tue, 22 Mar 2022 10:00:00 -0400 https://www.roofingcontractor.com/articles/96784-case-study-battling-extreme-weather-conditions-in-houston-with-owens-cornings-duration-series-shingles Cody Felts 6 A comparison of a job completed by Keystone Roofing & Construction after (top) and before (bottom) installing Owens Corning Duration shingles. Cody Felts 3 “The Houston weather can be really tough on roofs,” said Cody Felts, founder and owner of Keystone Roofing & Construction. “Granular loss is the primary problem. The conditions often loosen the protective layer of granules causing shingles to deteriorate or even leak over time.” Cody Felts 2 In addition to the quality of their efforts, Keystone prides itself on the ability to complete 90% of its roofing jobs in a single day. Cody Felts 1 Owens Corning shingles include SureNail® Technology, which provides a wide, highly visible engineered fabric strip for ensuring No-Guess nailing zones, outstanding gripping power and excellent fastening holding power against wind uplift. R/J Group Inc. shows how offering feasible repairs in place of total replacements not only saved the customer money, but led to additional work.

]]> http://www.roofingcontractor.com/articles/96347 Tue, 16 Nov 2021 10:00:00 -0500 https://www.roofingcontractor.com/articles/96347-case-study-reliable-cost-effective-roof-repairs-needed-for-beachside-condo-building r/j-group-case-study-condo-1 R/J Group, Inc. was able to design a repair method that would only cost Windward South around $20,000 and would include a one-year labor or workmanship warranty on the repairs rendered that are determined to be installation defects from the repairs. Photos: R/J Group Inc. r/j-group-case-study-condo-2 In September 2021, during an audit, R/J Group Inc. determined the main roof system at the Windward South is holding up very well and is currently in no need of additional repairs. r/j-group-case-study-condo-3 A before photo of the roof at the Windward South Condominiums in Florida before R/J Group's repairs. SALT Energy sought out S-5! products to install a solar system that can endure 180 mph Category 5 hurricane winds for the Ocean Reef Club in Key Largo.

]]> http://www.roofingcontractor.com/articles/96288 Mon, 01 Nov 2021 09:00:00 -0400 https://www.roofingcontractor.com/articles/96288-case-study-ocean-reef-club-at-key-largo ORCA-full-roof-S-5 SALT Energy turned to S-5! and its S-5-PVKIT 2.0 and RibBracket III to install a solar PV that can withstand Category 5 winds at the Ocean Reef Club in Key Largo. Photos courtesy of S-5!. ORCA-closeup-roof-S-5 The solar installation is predicted to save the resort on average $1,000 per month on its electric bills. H-POWER in Kapolei, West Oahu turned to metal roofing and attachment solutions offered by S-5! in one of Hawaii's largest rooftop solar projects.

]]> http://www.roofingcontractor.com/articles/95849 Wed, 07 Jul 2021 09:00:00 -0400 https://www.roofingcontractor.com/articles/95849-case-study-hawaii-h-power-solar-project S-5-Case-Study-Hawaii_1 The S-5-S Mini clamp was selected as the preferred attachment method to secure solar modules to the roof of the new H-POWER “solar building” to allow a penetration-free attachment for the solar racking system. Photos courtesy of S-5!. S-5-Case-Study-Hawaii_2 The newly constructed metal “solar building” had to be designed with cost-effective solutions for the long-term both for the PV project and various recycling programs within the building. S-5-Case-Study-Hawaii_3 The H-POWER plant and adjacent “solar building” utilized metal building components to achieve lasting performance and durability, while allowing the city to process and manage the island’s solid waste and convert trash to power. S-5-Case-Study-Hawaii_4 The entire project had to be completed within a tight timeframe and without disruption to H-POWER’s operations, which is a key component of the island’s waste management infrastructure. To upgrade a facility's 145,300 square foot roof with metal and solar while dealing with COVID delays, a contractor turned to S-5! to shrink the project timeline.

]]> http://www.roofingcontractor.com/articles/95622 Wed, 05 May 2021 09:00:00 -0400 https://www.roofingcontractor.com/articles/95622-case-study-microtechs-costa-rica-facility-goes-solar MicroTech-S-5_1 ELCA selected the S-5-PVKIT®2.0 and the S-5-H Mini clamps to secure the solar panels to the standing seam metal roof of MicroTech’s manufacturing facility, allowing for a rail-less PV mounting solution. Photos courtesy of S-5!. MicroTech-S-5_2 S-5!’s solar attachment solutions helped reduce the project timeline, which helped the contractor manage COVID-related delays and shutdowns. MicroTech-S-5_3 The H Mini clamp’s two-piece design allows it to be installed anywhere along the length of the rib. MicroTech-S-5_4 Energías Limpias de Centroamerica  installed a Micro-Grid that combined a Tesla PowerPack and 1,432 Sharp solar panels for a 531 kilowatt DC system on the facility’s insulated metal panel roof. A New York-based apple orchard chose to go metal and solar to supplement the farm’s power generation and achieve its goal of operating a net-zero farm.

]]> http://www.roofingcontractor.com/articles/95488 Fri, 26 Mar 2021 09:30:00 -0400 https://www.roofingcontractor.com/articles/95488-case-study-kc-bailey-orchards S-5-Bailey_Orchard_1 Five of the nine metal roofs feature direct-attach solar photovoltaics (PV). The PV was secured to the roofs with the S-5-PVKIT®2.0 solar attachment solution and S-5-S Mini clamps. The remaining, older structures utilize a traditional rail system. Photography by David Townsend. S-5-Bailey_Orchard_2 The Baileys chose to use metal building components not only for their lasting performance and durability but also because of their reflective properties, which lowers the temperature of the building and enhances its cold-storage functionality. Photography by David Townsend. S-5-Bailey_Orchard_3 The PVKIT mounting system was chosen to secure the solar panels to the metal roof because it provides a rail-less, aesthetically-pleasing, penetration-free, and cost-effective solar mounting solution. Photography by David Townsend. Not only did this project renovate a California church with a durable new roof, it earned third place in the 2019 ATAS Project of the Year competition.

]]> http://www.roofingcontractor.com/articles/95365 Wed, 24 Feb 2021 09:00:00 -0500 https://www.roofingcontractor.com/articles/95365-case-study-cornerstone-bible-church-renews-roof-with-metal-shingles 2019 ATAS Project of the Year Bronze For the Cornerstone Bible Church, two colors, Rocky Grey and Charcoal Grey, were used together to create an aesthetically pleasing pattern on the roof. Photos courtesy of ATAS International. 2019 ATAS Project of the Year Bronze_before A before shot of the old asbestos diamond shaped shingle roof of Cornerstone Bible Church in Glendora, Calif. 2019 ATAS Project of the Year Bronze_tearoff Dustyn Howard, president of Howard & Sons Inc. in Corona, Calif., stated that they removed the old asbestos shingles and the CastleTop metal panels were installed over a solid wood deck. The owner’s goal was to construct a multi-purpose building and rooftop solar system that would provide 100% of the electricity needs for their equestrian ranch property.

]]> http://www.roofingcontractor.com/articles/95266 Wed, 27 Jan 2021 11:21:00 -0500 https://www.roofingcontractor.com/articles/95266-case-study-canadian-equestrian-multi-purpose-barn solar-barn-canada-s-5_1 The 3,500-square-foot, multipurpose barn serves as a mounting platform for a 28.35 kilowatt PV solar system that powers the entire property. Photos courtesy of S-5!. solar-barn-canada-s-5_2 The owner specified a standing seam metal roof for its sustainability and durability, since it is the only roof type with a service life that actually exceeds the service life of a solar PV system. solar-barn-canada-s-5_3 The ridge line of the barn roof was oriented exactly due east/west, to afford maximum solar gain for the 90 solar panel system mounted on the south-facing upper roof and lower roof surfaces.  solar-barn-canada-s-5_4 The S-5-PVKIT 2.0 solar solution (in black to match the black anodized PV frames) enabled solar installers to direct-attach PV modules to the standing seams, eliminating the need for a traditional rail mounting system. Colorado Custom Metal Inc. was selected as the roofing contractor to reroof the museum with help from S-5! for snow retention.

]]> http://www.roofingcontractor.com/articles/95176 Fri, 25 Dec 2020 09:00:00 -0500 https://www.roofingcontractor.com/articles/95176-case-study-wings-over-the-rockies-air-space-museum S-5-case-study-air-space-museum_1 The roof of the Wings Over the Rockies Air & Space Museum was retrofitted with 92,400 square feet of curved standing seam roofing using the New Tech Series SSQ II MultiPro Roof Panel Machine with 675 tooling. Photos courtesy of S-5!. S-5-case-study-air-space-museum_2 S-5-case-study-air-space-museum_3 S-5-case-study-air-space-museum_4 Students and faculty heading back to school in the Milwaukee Public School district have one less thing to worry about thanks to the district’s longstanding partnership with Atlas Roofing Corporation.

]]> http://www.roofingcontractor.com/articles/94852 Thu, 03 Sep 2020 09:00:00 -0400 https://www.roofingcontractor.com/articles/94852-video-case-study-back-to-school-in-the-milwaukee-school-district Between strict energy codes and residing in a high-wind area, installing solar on a multi-roof family compound in Boulder, Colo. proved to be a challenge.

]]> http://www.roofingcontractor.com/articles/94736 Fri, 31 Jul 2020 09:00:00 -0400 https://www.roofingcontractor.com/articles/94736-case-study-colorado-compound-receives-solar-on-multiple-rooftops S-5!® ColorGard® on a standing seam metal roof and the S-5-S clamp Photos courtesy of S-5!. PVKIT2.0andColorgard PVKIT2.0 and S-5! Colorgard. CalcaireHouse s-5 The Calcaire House consists of three roofs with a roof pitch of 10 x 12. Atlas partnered with the KU School of Architecture & Design and the nonprofit Studio 804 to help graduate students design and build a sustainable home for a final project.

]]> http://www.roofingcontractor.com/articles/94645 Tue, 23 Jun 2020 10:30:00 -0400 https://www.roofingcontractor.com/articles/94645-case-study-atlas-roofing-partners-with-university-of-kansas-students-for-real-world-construction-experience 1_Atlas Roofing Photos_Page 2_Atlas Roofing Photos_Page 3_Atlas Roofing Photos_Page 4_Atlas Roofing Photos_Page dkramer@icynene-lapolla.com (Doug Kramer) http://www.roofingcontractor.com/articles/94527 Fri, 08 May 2020 15:17:40 -0400 https://www.roofingcontractor.com/articles/94527-case-study-tricky-michigan-roof-receives-new-life-with-spray-foam CS_Img01.jpg Spray Tight Foam Insulators selected Icynene-Lapolla’s high-performance, closed-cell system to provide both waterproofing and thermal insulation to this manufacturing facility in River Rouge, Mich. Weather resiliency was a major factor in the three-month project in a region where extreme cold, wind and rain are a given, and often relentless. Photos courtesy of Icynene-Lapolla. CS_Img02.jpg Spray Tight Foam Insulators selected Icynene-Lapolla’s high-performance, closed-cell system to provide both waterproofing and thermal insulation to this manufacturing facility in River Rouge, Mich. Weather resiliency was a major factor in the three-month project in a region where extreme cold, wind and rain are a given, and often relentless. Photos courtesy of Icynene-Lapolla. CS_Img03.jpg Spray Tight Foam Insulators selected Icynene-Lapolla’s high-performance, closed-cell system to provide both waterproofing and thermal insulation to this manufacturing facility in River Rouge, Mich. Weather resiliency was a major factor in the three-month project in a region where extreme cold, wind and rain are a given, and often relentless. Photos courtesy of Icynene-Lapolla. rickdamato@yahoo.com (Rick Damato) The best time to perform any significant work on a school building is when school is out, but that was not possible in the case of Rome High School in Georgia.

]]> http://www.roofingcontractor.com/articles/93615 Mon, 15 Apr 2019 00:00:00 -0400 https://www.roofingcontractor.com/articles/93615-case-study-reroofing-at-georgia-schools-completed-as-classes-continue Rome-High-School-2-b.jpg The Rome Schools reroofing project was among the largest ever worked on by Ben Hill Roofing Inc., of Douglasville, Ga., and completed while classes remained in session. Photos by Rick Damato BHR-Rome-Middle-School-2.jpg Crews from Ben Hill Roofing reroofed roughly 3,000 squares of metal standing-seam steel panels at the Rome Middle and High School campus in Rome, Ga. Rome-High-School-40.jpg The Rome Schools reroofing project was among the largest ever worked on by Ben Hill Roofing Inc., of Douglasville, Ga., and completed while classes remained in session. Rome-High-School-77.jpg (From left) Johnny Rogers, project manager of Ben Hill Roofing; Joe Wade, superintendent, J&R Construction; Roger Gray, general production manager; Jake Balcombe, superintendent; and David Welch, president at Ben Hill Roofing, were onsite for the completion of the Rome Schools roofing project last year. Rome-Schools-complete---drone-1.jpg The Rome Schools reroofing project was among the largest ever worked on by Ben Hill Roofing Inc., of Douglasville, Ga., and completed while classes remained in session. http://www.roofingcontractor.com/articles/91932 Mon, 05 Dec 2016 00:00:00 -0500 https://www.roofingcontractor.com/articles/91932-the-moose-hotel-suites-debuts-in-picturesque-banff-with-distinctive-roong-tile PNW-Slate-Mission-Red-MooseHotel-main-900x550.jpg Photos courtesy of Boral Roofing. banff-slide2.jpg Photos courtesy of Boral Roofing. banff-slide3.jpg Photos courtesy of Boral Roofing. banff-slide4.jpg Photos courtesy of Boral Roofing. banff-slide5.jpg Photos courtesy of Boral Roofing. http://www.roofingcontractor.com/articles/91340 Mon, 04 Jan 2016 12:00:00 -0500 https://www.roofingcontractor.com/articles/91340-atlas-answers-the-call-for-our-veterans-at-camp-liberty http://www.roofingcontractor.com/articles/91187 Wed, 02 Sep 2015 00:03:00 -0400 https://www.roofingcontractor.com/articles/91187-a-walk-in-roofing-contractors-shoes-red-wing-shoe-company-plant-1-blends-history-and-new-tpo-roofing-system http://www.roofingcontractor.com/articles/90470 Thu, 10 Jul 2014 00:00:00 -0400 https://www.roofingcontractor.com/articles/90470-rooftop-pipe-and-equipment-supports-that-deliver