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 $6.5 million and $5.5 million for the three months ended September 30, 2021 and 2020, respectively, and $20.6 million and $18.2 million for the nine months ended September 30, 2021 and 2020, respectively, for all plans. An accrual for estimated healthcare claims incurred but not reported (“IBNR”) is included within accrued compensation on the Condensed Consolidated Balance Sheets and was $3.2 million and $3.1 million as of September 30, 2021 and December 31, 2020, respectively.

Workers’ compensation expense totaled $4.8 million and $4.1 million for the three months ended September 30, 2021 and 2020, respectively, and $11.9 million and $11.4 million for the nine months ended September 30, 2021 and 2020, respectively. Workers’ compensation known claims and IBNR reserves included on the Condensed Consolidated Balance Sheets were as follows (in thousands):


	September 30, 2021		December 31, 2020
Included in other current liabilities	$	6,775	$	7,703
Included in other long-term liabilities	12,490		11,986
	$	19,265	$	19,689

We also had an insurance receivable for claims that exceeded the stop loss limit under our self-insured policies as well as claims under our fully insured policies included on the Condensed 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. We recognized 401(k) plan expenses of $0.5 million and $0.4 million during the three months ended September 30, 2021 and 2020, respectively, and $1.9 million and $1.6 million during the nine months ended September 30, 2021 and 2020, respectively. These expenses are included in administrative expenses on the accompanying Condensed 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.

We periodically grant shares of our common stock to non-employee members of our board of directors and our employees. During the nine months ended September 30, 2021 and 2020, we granted approximately four thousand and six thousand shares of our common stock, respectively, under our 2014 Omnibus Incentive Plan to non-employee members of our board of directors. The stock will vest over a one year service period.

In addition, we granted approximately seven thousand and three thousand shares during the three months ended September 30, 2021 and 2020, respectively and 0.1 million and 0.2 million shares of our common stock to employees during the nine months ended September 30, 2021 and 2020, respectively.

During the nine months ended September 30, 2021, we issued approximately 0.1 million shares of our common stock to certain officers, which vest in two equal installments on each of April 20, 2022 and April 20, 2023. In addition, during the nine months ended September 30, 2021, we established, and our board of directors approved, performance-based targets in connection with common stock awards to be issued to certain officers in 2022 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 in the first quarter of 2022 and as such are included in other current liabilities on the Condensed Consolidated Balance Sheets. During the nine months ended September 30, 2021 and 2020, we granted approximately five thousand and seven thousand shares of our common stock, respectively, all of which will vest in 2022.

During 2020, 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 2021 based upon achievement of a performance target. In

addition, during the nine months ended September 30, 2021, 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 2022 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.


	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, 2020	231,280	$	48.05	166,961	$	59.97	13,273	$	36.51
Granted	55,815	124.88		42,449	123.32		8,470	126.89
Vested	(84,254)	48.81		(64,525)	52.79		(12,952)	36.51
Forfeited/Cancelled	(2,448)	57.85		—	—		(488)	67.44
Nonvested awards/units at September 30, 2021	200,393	$	69.01	144,885	$	81.73	8,303	$	126.89


	Three months ended September 30,				Nine months ended September 30,
	2021		2020		2021		2020
Common Stock Awards	$	1,426	$	997	$	3,843	$	3,006
Non-Employee Common Stock Awards	126		104		339		230
Performance-Based Stock Awards	1,128		928		3,462		2,844
Liability Performance-Based Stock Awards	598		488		1,983		1,554
Performance-Based Restricted Stock Units	257		118		601		416
	$	3,535	$	2,635	$	10,228	$	8,050


	Three months ended September 30,				Nine months ended September 30,
	2021		2020		2021		2020
Cost of sales	$	161	$	60	$	287	$	221
Selling	56		45		145		154
Administrative	3,318		2,530		9,796		7,675
	$	3,535	$	2,635	$	10,228	$	8,050

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.


	As of September 30, 2021
	Unrecognized Compensation Expense on Unvested Awards		Weighted Average Remaining Vesting Period
Common Stock Awards	$	9,201	1.8 years
Performance-Based Stock Awards	6,082		1.7 years
Performance-Based Restricted Stock Units	553		0.5 years
Total unrecognized compensation expense related to unvested awards	$	15,836

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 nine months ended September 30, 2021 and 2020, our employees surrendered approximately 43 thousand and 25 thousand shares of our common stock, respectively, to satisfy tax withholding obligations arising in connection with the vesting of common stock awards issued under our 2014 Omnibus Incentive Plan. We recognized windfall tax benefits of $3.0 million for the nine months ended September 30, 2021 and we recognized a tax shortfall of $0.3 million for the nine months ended September 30, 2020 within the income tax provision in the Condensed Consolidated Statements of Operations and Comprehensive Income.

As of September 30, 2021, approximately 1.9 million of the 3.0 million shares of common stock authorized for issuance were available for issuance under the 2014 Omnibus Incentive Plan.