We participate in multiple healthcare plans, the largest of which is partially self-funded with an insurance company paying benefits in excess of stop loss limits per individual/family. Our healthcare benefit expense (net of employee contributions)

was approximately $24.1 million, $21.9 million and $17.8 million for the years ended December 31, 2020, 2019 and 2018, respectively, for all plans. An accrual for estimated healthcare claims incurred but not reported (“IBNR”) is included within accrued compensation on the Consolidated Balance Sheets and was $3.1 million and $2.6 million as of December 31, 2020 and 2019, respectively.

We participate in multiple workers’ compensation plans. Under these plans, for a significant portion of our business, we use a high deductible program to cover losses above the deductible amount on a per claim basis. We accrue for the estimated losses occurring from both asserted and unasserted claims. Workers’ compensation liability for premiums is included in other current liabilities on the Consolidated Balance Sheets. Insurance claims and reserves include accruals of estimated settlements for known claims, as well as accruals of actuarial estimates of IBNR claims. In estimating these reserves, historical loss experience and judgments about the expected levels of costs per claim are considered. These claims are accounted for based on actuarial estimates of the undiscounted claims, including IBNR. We believe the use of actuarial methods to account for these liabilities provides a consistent and effective way to measure these highly judgmental accruals.

Workers’ compensation expense totaled $15.7 million, $15.4 million and $12.8 million for the years ended December 31, 2020, 2019 and 2018, respectively, and is included in cost of sales on the Consolidated Statements of Operations and Comprehensive Income. Workers’ compensation known claims and IBNR reserves included on the Consolidated Balance Sheets were as follows (in thousands):

We also had an insurance receivable for claims that exceeded the stop loss limit for fully insured policies included on the Consolidated Balance Sheets. This receivable offsets an equal liability included within the reserve amounts noted above and was as follows (in thousands):

We participate in multiple 401(k) plans, whereby we provide a matching contribution of wages deferred by employees and can also make discretionary contributions to each plan. Certain plans allow for discretionary employer contributions only. These plans cover substantially all our eligible employees. During the years ended December 31, 2020, 2019 and 2018, we recognized 401(k) plan expenses of $2.2 million, $2.0 million and $1.7 million, respectively, which is included in administrative expenses on the accompanying Consolidated Statements of Operations and Comprehensive Income.

We participate in various multiemployer pension plans under collective bargaining agreements in Washington, Oregon and Illinois with other companies in the construction industry. These plans cover our union-represented employees and contributions to these plans are expensed as incurred. These plans generally provide for retirement, death and/or termination benefits for eligible employees within the applicable collective bargaining units, based on specific eligibility/participation requirements, vesting periods and benefit formulas. We do not participate in any multiemployer pension plans that are considered to be individually significant.

•If a participating employer chooses to stop participating in these multiemployer plans, the employer may be required to pay those plans a withdrawal liability based upon the underfunded status of the plan.

We also participate in various multiemployer health and welfare plans that cover both active and retired participants. Health care benefits are provided to participants who meet certain eligibility requirements under the applicable collective bargaining unit.

The increase in contributions for the year ended December 31, 2020 was driven by the acquisitions of Insulation Contractors/Magellan Insulation and Norkote, Inc. See Note 17, Business Combinations for more information.

We periodically grant shares of our common stock under our 2014 Omnibus Incentive Plan to non-employee members of our board of directors and our employees. During the years ended December 31, 2020, 2019 and 2018 , we granted approximately six thousand, eight thousand and five thousand shares of restricted stock, respectively, to non-employee members of our board of directors. Substantially all of the stock will vest over a one-year service period.

In addition, we granted approximately 0.2 million, 0.1 million and 0.1 million shares of our common stock to employees in each of the years ended December 31, 2020, 2019 and 2018, respectively. Substantially all of the stock will vest in three equal installments (rounded to the nearest whole share) annually over a three-year service period.

We periodically grant nonvested stock awards subject to performance-based vesting conditions to certain officers. During the year ended December 31, 2020, we issued approximately 0.1 million shares of our common stock which vest in two equal installments on each of April 20, 2021 and April 20, 2022. In addition, during the year ended December 31, 2020, we established, and our Board of Directors approved, performance-based targets in connection with common stock awards to be issued to certain officers in 2021 contingent upon achievement of these targets.

In addition, there are long-term performance-based restricted stock awards to be issued to certain employees annually through 2022 contingent upon achievement of certain performance targets. These awards are accounted for as liability-based awards since they represent a predominantly-fixed monetary amount that will be settled with a variable number of common shares and as such are included in other long-term liabilities on the Consolidated Balance Sheets. During the year ended December 31, 2020, we granted approximately seven thousand shares that will vest in 2022.

During 2019, we established, and our board of directors approved, performance-based restricted stock units in connection with common stock awards which were issued to certain employees in 2020 based upon achievement of a performance target. In addition, during the year ended 2020, we established, and our board of directors approved, performance-based restricted stock units in connection with common stock awards to be issued to certain employees in 2021 based upon achievement of a

performance target. These units will be accounted for as equity-based awards that will be settled with a fixed number of common shares. During the year ended December 31, 2020, we granted approximately fourteen thousand shares that will vest over a one-year service period.


	Common Stock Awards			Performance-Based Stock Awards			Performance-Based Restricted Stock Units
	Awards	Weighted Average Grant Date Fair Value Per Share		Awards	Weighted Average Grant Date Fair Value Per Share		Units	Weighted Average Grant Date Fair Value Per Share
Nonvested awards/units at December 31, 2019	152,882	$	52.93	160,289	$	50.49	13,186	$	51.62
Granted	174,445	44.56		61,174	77.20		13,655	36.51
Vested	(90,870)	49.69		(54,502)	51.43		(13,077)	51.50
Forfeited/Cancelled	(5,177)	45.94		—	—		(491)	42.94
Nonvested awards/units at December 31, 2020	231,280	$	48.05	166,961	$	59.97	13,273	$	36.51


	Years ended December 31,
	2020		2019		2018
Common Stock Awards	$	4,116	$	4,242	$	3,847
Non-Employee Common Stock Awards	333		359		177
Performance-Based Stock Awards	3,869		3,034		2,041
Liability Performance-Based Stock Awards	1,969		432		163
Performance-Based Restricted Stock Units	539		660		1,618
	$	10,826	$	8,727	$	7,846

Administrative stock compensation expense includes all stock compensation earned by our administrative personnel, while cost of sales and selling stock compensation represents all stock compensation earned by our installation and sales employees, respectively. We recognized a tax shortfall of $0.3 million for the year ended December 31, 2020 and we recognized windfall tax benefits of $0.3 million and $0.5 million for the years ended December 31, 2019 and 2018, respectively, associated with our Common Stock Awards within the income tax provision in the Consolidated Statements of Operations and Comprehensive Income.


	As of December 31, 2020
	Unrecognized Compensation Expense on Unvested Awards		Weighted Average Remaining Vesting Period
Common Stock Awards	$	7,162	1.9 years
Performance-Based Stock Awards	4,310		1.6 years
Performance-Based Restricted Stock Units	137		0.3 years
Total unrecognized compensation expense related to unvested awards	$	11,609

Total unrecognized compensation expense is subject to future adjustments for forfeitures. This expense is expected to be recognized over the remaining weighted-average period shown above on a straight-line basis except for the Performance-Based Stock Awards which uses the graded-vesting method. Shares forfeited are returned as treasury shares and available for future issuances.

During the years ended December 31, 2020, 2019 and 2018, our employees surrendered approximately 25 thousand, 45 thousand and 41 thousand shares of our common stock under all plans, respectively, to satisfy tax withholding obligations arising in connection with the vesting of common stock awards issued under our 2014 Omnibus Incentive Plan.